Tab molecules

ABSTRACT

The present invention relates to TAB molecules, ADEPT constructs directed against TAG-72, and their use in therapy.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Patent Application Ser. No. 60/675,728, entitled “TAB Molecules”, filed Apr. 28, 2005.

FIELD OF THE INVENTION

The present invention relates to TAB molecules, ADEPT constructs directed against TAG-72 and their use in therapy.

BACKGROUND

Traditional non-targeted therapeutics circulate freely throughout the body of patients until removed from circulation. Such non-targeted molecules exert effects indiscriminately on a wide range of cells and tissues, which can cause serious side effects. When the therapeutic is toxic (e.g., a chemotherapeutic, where the “therapeutic window,” the difference between an efficacious and injurious or even lethal dose, is small), the problem is particularly acute.

Researchers have attempted to develop therapeutics specific for a particular tissue. Most target particular tissues by preferentially binding a target displayed by the tissue. By targeting diseased tissues, the therapeutic window is increased and side effects reduced.

Preferential binding is employed in antibody-directed enzyme prodrug therapy ((ADEPT); See, e.g., Xu et al., 2001, Clin Cancer Res. 7:3314-24; Denny, 2001, Eur J Med. Chem. 36:577-95). In ADEPT, an antibody or antibody fragment is linked to an enzyme capable of converting an inactive prodrug into an active cytotoxic, producing an ADEPT conjugate. The conjugate is administered to the patient and localizes to a target tissue via antibody/antigen binding. An inactive prodrug is subsequently administered, and the prodrug circulates throughout the patient's body, but causes few or no side effects because the prodrug is inactive until activated by the conjugate only in the vicinity of the tissue. Thus, the therapeutic window of the toxin is increased at the desired site, as a relatively low concentration of active drug is present throughout the body, but a relatively high concentration of active drug is produced in the vicinity of the target tissue.

In ADEPT, selecting the proper antigen is important (e.g., an antigen that has a high tumor/normal expression profile). A tumor antigen of particular interest is TAG-72, frequently found on the cell surface in cancer tissues. TAG-72 is mainly a carbohydrate epitope expressed on a variety of human adenocarcinomas, but showing low expression in most normal tissues [Cao, Y., P. Stosiek, G. F. Springer and U. Karsten (1996) Histochem Cell Biol 106, 197-207, Thomsen-Friedenreich-related carbohydrate antigens in normal adult human tissues: a systematic and comparative study].

SUMMARY OF THE INVENTION

The present invention relates to TAB molecules, ADEPT constructs directed against TAG-72 and their use in therapy, especially with prodrugs as described herein. The molecules of the current invention have been preferably deimmunized and do not elicit an immune response and can be produced in high yield. In a first aspect, the TAB molecule comprises an antibody/enzyme conjugate. In a preferred embodiment, the TAB molecule comprises an scFv, and the scFv has an unmodified amino acid sequence, the amino acid sequence comprising the sequence set forth in SEQ ID NO: 2. In a preferred embodiment, the TAB molecule has an amino acid sequence modified from the amino acid sequence set forth in SEQ ID NO: 2, the modification comprising at least one position selected from group consisting of: h8, h57, h62, h80, 15, 153, 179 and 1105, the h and 1 in front of each designated position denoting a heavy or light chain, respectively, wherein numbering is with respect to the scFv set forth in SEQ ID NO: 2 based on the Kabat system (see, for example, Wu, T. T. and E. A. Kabat (1970) J. Exp. Med. 132, 211-250). In a preferred embodiment, the TAB molecule is modified at the following positions: h80, 15, 153 and 179. In a preferred embodiment, the TAB molecule has the following modifications: hV80L,1S5T, 1A53T and 1K79E. In a preferred embodiment, the TAB molecule comprises a TAB2.4, TAB2.5 or TAB2.8 molecule, the TAB2.4, TAB2.5 or TAB2.8 molecule comprising SEQ ID NO: 2, SEQ ID NO: 20 or SEQ ID NO: 22, respectively.

In a preferred embodiment, the TAB molecule further comprises an enzyme. In a preferred embodiment, the enzyme comprises a BLA.

In a preferred embodiment, the TAB molecule comprises a full-length antibody/enzyme TAB conjugate, and the scFv has an unmodified amino acid sequence, the amino acid sequence comprising the sequence set forth in SEQ ID NO: 6, SEQ ID NO: 8 or SEQ ID NO: 12. In a preferred embodiment, the TAB molecule has an amino acid sequence modified from the amino acid sequence set forth in SEQ ID NO: 8, the modification comprising at least one position selected from group consisting of: h8, h57, h62, h80, 15, 153, 179 and 1105, the h and 1 in front of each designated position denoting a heavy or light chain, respectively, wherein numbering is with respect to the scFv set forth in SEQ ID NO: 2, based on the Kabat system (see, for example, Wu, T. T. and E. A. Kabat (1970) J. Exp. Med. 132, 211-250). In a preferred embodiment, the TAB molecule is modified at the following positions: h80, 15, 153 and 179. In a preferred embodiment, the TAB molecule has the following modifications: hV80L, 1S5T, 1A53T and 1K79E. In a preferred embodiment, the TAB molecule comprises a TAB2.4, TAB2.5 or TAB2.8 molecule, the TAB2.4, TAB2.5 or TAB2.8 molecule comprising SEQ ID NO: 8, SEQ ID NO: 10 or SEQ ID NO:16, respectively.

In a preferred embodiment, the molecule comprises TAB2.6 having SEQ ID NO: 12. In a preferred embodiment, the molecule comprises clone ME374.4, ME375.18, ME374.31, ME374.63, ME374.73 or ME375.69.

In a second aspect, the invention is drawn to a nucleic acid encoding a TAB conjugate as set forth in any of the embodiments of the first Aspect, as well as those provided in the description, herein.

In a preferred embodiment, the molecule is a nucleic acid comprising one of the following sequences: SEQ ID NO: 7, SEQ ID NO: 9, SEQ ID NO: 11 or SEQ ID NO: 13.

In a third aspect, the invention is drawn to treating a subject in need thereof, comprising administering to the subject a TAB molecule, as provided herein, and a prodrug that is a substrate of the TAB molecule. In a fourth aspect, the invention is drawn to a pharmaceutical composition comprising a TAB molecule.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows relevant amino acid sequences set forth in the invention. FIG. 1A shows the amino acid sequence for TAB2.4 (SEQ ID NO: 8). The vH and vL sequences are underlined, the linker between vH and vL is in bold. FIG. 1B shows the protein sequence for CC49 (SEQ ID NO: 3). FIG. 1C sets forth the BLA portion of TAB2. FIG. 1D sets forth the amino acid sequence for TAB2.1 (SEQ ID NO: 6). FIG. 1E sets forth the DNA sequence for TAB2.1 (SEQ ID NO: 5). FIG. 1F sets forth the amino acid sequence for TAB2.4 (SEQ ID NO: 8). FIG. 1G sets forth the nucleotide sequence for TAB2.4 (SEQ ID NO: 7). FIG. 1H sets forth the amino acid sequence for TAB2.5 (SEQ ID NO: 10). FIG. 1I sets forth the nucleotide sequence for TAB2.5 (SEQ ID NO: 9). FIG. 1J sets forth the amino acid sequence for TAB2.6 (SEQ ID NO: 12). FIG. 1K sets forth the nucleotide sequence for TAB2.6 (SEQ ID NO: 11). FIG. 1L sets forth the amino acid sequence for TAB2.7 (SEQ ID NO: 14). FIG. 1M sets forth the nucleotide sequence for TAB2.7 (SEQ ID NO: 13). FIG. 1N sets forth the amino acid sequence for the pME403.3 protein (SEQ ID NO: 18). FIG. 10 sets forth the nucleotide sequence encoding the pME403.3 protein (SEQ ID NO: 17). FIGS. 1P and 1Q set forth the amino acid and nucleotide sequences, respectively, for the TAB2.8 molecule (SEQ ID NO: 16 and SEQ ID NO: 15, respectively).

FIG. 2 shows the screening data for binding to coated BSM, the data showing clones from libraries ME367 (top) and ME368 (bottom), as set forth in Example 4. The x-axis shows the colony number, and the y-axis shows bound BLA.

FIG. 3 sets forth the statistical analysis of the screening data versus sequencing of clones from libraries ME367 and ME368, as set forth in Example 4.

FIG. 4 shows the screening data for binding to coated BSM as opposed to BLA activity of clones from libraries ME374, ME375 and ME377, as set forth in Example 4. Many clones in the libraries are wild type TAB2.4 and are shown by squares. The x-axis shows input BLA activity, and the y-axis shows BSM antigen-binding units. Clones located to the right express more BLA activity and clones higher than the average diagonal trend bind better to coated BSM so that the output/input ratio of BLA activity is higher then average. The inset shows clone codes used.

FIG. 5 shows the statistical analysis of screening data as opposed to sequencing of clones from libraries ME374, ME375 and ME368, as set forth in Example 4. The x-axis shows the clone number, and the y-axis shows the parameter [for the statistical algorithm, please see, Amin, N., A. D. Liu, S. Ramer, W. Aehle, D. Meijer, M. Metin, S. Wong, P. Gualfetti and V. Schellenberger (2004) Protein Eng Des Sel 17, 787-93, Construction of stabilized proteins by combinatorial consensus mutagenesis].

FIG. 6 shows screening of 22 clones from TAB2.4 consensus combinatorial mutagenesis, as set forth in Example 4. The data show the ratio of the value for the clone over TAB2.4, wild-type for expression, BSM binding or off-rate. A value >1 means that the clone has better expression, BSM binding than parent TAB2.4, while a value <1 means that the clone has a lower expression, BSM binding or off-rate. The x-axis shows clone number, and the y-axis shows variant screening relative to wild-type.

FIG. 7 shows expression in a 25 mL shake flask of various clones from the combinatorial consensus mutagenesis library screening, as set forth in Example 4. The x-axis sets forth the clone number, and the y-axis shows BLA activity.

FIG. 8 shows a Western blot using an anti-BLA antibody for various TAB2.4 variants from the screening of the combinatorial consensus mutagenesis library, as set forth in Example 4. The top panel shows the Western, the bottom panel contains a chart setting forth mutations present in each of the clones.

FIG. 9 sets forth the binding of various TAB variants coated to BSM, as set forth in Example 4. The x-axis shows BLA activity, in units, and the y-axis shows BSM antigen binding units. The inset shows clone codes used.

FIG. 10 shows an SDS-PAGE of purified monomer of TAB2.4 after endotoxin removal as set forth in Example 5. Lane 1: molecular weight standard; Lanes 3-4: purified TAB2.4

FIG. 11 shows binding of TAB2.5 to various coated TAG-72 antigens, as set forth in Example 6. The x-axis shows BLA added, measured in units. The y-axis shows bound BLA.

FIG. 12 shows TAB2.4 and TAB2.5 binding to coated BSM, as set forth in Example 6. The x-axis shows BLA added. The y-axis shows bound BLA.

FIG. 13 shows a measurement of off-rate of TAB2.4 and TAB2.5 coated to BSM, as set forth in Example 6. The x-axis shows time, in minutes, and the y-axis shows fraction bound.

FIG. 14 shows competition binding of TAB2.5 to coated tumor extract (TE), by BSM, TE, CA72-4 and TAG-72 multimer, as set forth in Example 6. The x-axis shows the respective protein, and the y-axis shows percent bound.

FIG. 15 shows competition binding of TAB2.5 to coated BSM by BSM, TE, CA72-4 and TAG-72 multimer, as set fort in Example 6. The x-axis shows respective protein, and the y-axis shows percent bound.

FIG. 16 shows screening data for binding to coated BSM as opposed to input activity of clones from libraries ME384-ME387, as set forth in Example 8. Many clones in the libraries were parent TAB2.5 clones and are shown by black squares. Clones picked were as similar as possible to the TAB2.5 average. The x-axis shows BLA input, and the y-axis shows BSM binding. Inset shows respective clone codes. Clones located to the right express more BLA activity and clones higher than the average diagonal trend bind better to coated BSM so that the output/input ratio of BLA activity is higher then average.

FIG. 17 shows the effect of thermolysin treatment for 1 hour at 37° C. on the BLA activity of TAB2.5 and TAB2.7, as set forth in Example 10. The x-axis shows protease added, and the y-axis shows fraction of BLA activity remaining TAB2.5 is shown in white circles and TAB2.7 is shown in dark circles. The inset shows clone codes used.

FIG. 18 shows the effect of thermolysin treatment for 1 hour at 37° C. on the binding of TA2.7 to coated BSM, as set forth in Example 10. The x-axis shows BLA added, and the y-axis shows TAB2.7 binding.

FIG. 19 shows the binding of TAB2.7 and pME403.3 to coated BSM, as set forth in Example 11. The x-axis shows BLA added, and the y-axis shows BSM binding.

FIG. 20 shows differential scanning calorimeter (DSC) thermograms of TAB2.4 and TAB2.5, as set forth in Example 12. The x-axis shows temperature in ° C., and the y-axis shows CP (cal/° C.).

FIG. 21 shows immunohistochemistry of TAB2.5 on an Accumax A301 various cancer array (Pentagen), as set forth in Example 13.

FIG. 22 shows an immunohistochemistry of TAB2.5 on an Accumax A203 colon cancer array (Pentagen), as set forth in Example 13.

FIG. 23 shows an immunohistochemistry of TAB2.5 on an Accumax A203 colon cancer array (Pentagen), with magnification of a human colon cancer adenocarcinoma, as set forth in Example 13.

FIG. 24 shows TAB2.4 concentration-time profiles in mice, as set forth in Example 14, the x-axis showing time, in hours, and the y-axis showing TAB2.4 concentration in μg/ml.

FIG. 25 shows plasma TAB2.5 concentration-time profiles in rats, as set forth in Example 15. Actual TAB2.5 doses for each rat received: rat 1=0.85 mg/kg, rat 2=0.8 mg/kg and rat 3=0.4 mg/kg. The x-axis shows time in hours, and the y-axis shows TAB2.5 concentration in μg/ml.

FIG. 26 shows an efficacy study of TAB2.5 in an LS174T xenograph mouse model, as set forth in Example 16. The x-axis shows time in days, and the y-axis shows tumor volume, measured in mm³

FIG. 27 shows TAB2.8 binding, as set forth in Example 18.

DETAILED DESCRIPTION OF THE INVENTION

Unless defined otherwise, all technical and scientific terms used have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described can be used in the practice or testing of the present invention, the preferred methods and materials are described. For purposes of the present invention, the following terms are used as described below.

As used herein, “conjugate” shall mean an ADEPT molecule that binds selectively to an antigen of interest. Examples of conjugates are antibody or antibody fragments conjugated to an enzyme of particular interest, for example a BLA, as set forth herein.

As used herein, “antigen” is a chemical structure recognized by an antibody, also sometimes referred to as an epitope. Of particular interest are tumor associated antigens, sometimes referred to as TAAs.

As used herein, “target” shall mean a group of cells, a tissue, an organ, cancer cells or tumor tissue. In that sense, a target is a region of the body to which one would like to specifically deliver compounds, for example as specifically set forth herein.

“TAB” molecule shall mean a conjugate that binds to a TAG-72 antigen (“TAG-72”). A TAB molecule may have an unmodified sequence or a modified sequence, wherein the unmodified sequence comprises the amino acid sequence set forth in SEQ ID NO: 2. The unmodified or modified sequence can also include BLA.

As used herein, an “unmodified” sequence shall refer to a sequence that has not been modified, either comprising an scFv or comprising an entire conjugate.

A “modified” sequence refers to a sequence that includes at least one mutation with respect to an unmodified sequence, as set forth above. Position numbering shall be with respect to the particular embodiment described. For example, relative position numbering with respect to an scFv is often with respect to SEQ ID NO: 2, as provided above. Likewise, for example, relative position numbering in this document with respect to the entire conjugate is often with respect to SEQ ID NO: 8. The relative position of an amino acid or mutation in an antibody or antibody fragment is often described by the Kabat numbering system [Wu, T. T. and Kabat, E. A. (1970) Biochem J 250, 753-760., Sequence and comparative analysis of three Enterobacter cloacae amp-C beta-lactamase genes and their products].

As used herein, “BLA” shall mean a protein that is able to cleave lactam or cephalosporin structures. Of particular interest are BLAs that can activate prodrugs that contain a lactam or cephalosporin structure. For example, BLA from Enterobacter cloacae are of interest, as well as homologs [see, for example, Galleni, M., Lindberg, F., Normark S., Cole. S., Honore, N., Joris, B. and Frere, J. M. (1988). Sequence and comparative analysis of three Enterobacter cloacae ampC beta-lactamase genes and their products. Biochem J. 250, 753-760] as well as TEM-4 lactamase [Sirot, D. (1995) Extended-spectrum plasmid-mediated beta-lactamases] and enzymes homologous to TEM-4.

BLA has been reported to activate a variety of prodrugs to release commonly used cancer drugs such as doxorubicin [Vrudhula, V. M., H. P. Svensson and P. D. Senter (1995) J Med Chem 38, 1380-5, Cephalosporin derivatives of doxorubicin as prodrugs for activation by monoclonal antibody-beta-lactamase conjugates], vinblastin [Meyer, D. L., L. N. Jungheim, K. L. Law, S. D. Mikolajczyk, T. A. Shepherd, D. G. Mackensen, S. L. Briggs and J. J. Starling (1993) Cancer Res 53, 3956-63, Site-specific prodrug activation by antibody-beta-lactamase conjugates: regression and long-term growth inhibition of human colon carcinoma xenograft models], paclitaxel [Vrudhula, V. M., D. E. Kerr, N. O, Siemers, G. M. Dubowchik and P. D. Senter (2003) Bioorg Med Chem Lett 13, 539-42, Cephalosporin prodrugs of paclitaxel for immunologically specific activation by L-49-sFv-beta-Lactamase fusion protein] and melphalan [Vrudhula, V. M., P. D. Senter, K. J. Fischer and P. M. Wallace (1993) J Med Chem 36, 919-23, Prodrugs of doxorubicin and melphalan and their activation by a monoclonal antibody-penicillin-G amidase conjugate].

A “binding moiety” is a part of an ADEPT construct, e.g., TAB molecule that binds a target. In the current invention, the binding moiety of a TAB molecule binds TAG72. A binding moiety can comprise more than one region, either contiguous or non-contiguous, of a TAB molecule.

An “active moiety” is a part of an ADEPT construct, e.g., TAB molecule that confers functionality to the agent. An active moiety can comprise more than one region, either contiguous or non-contiguous, of, for example, a TAB molecule. In particular, an active moiety can be an enzyme such as beta-lactamase.

The terms “cell”, “cell line”, and “cell culture” can be used interchangeably and all such designations include progeny. All progeny may not be precisely identical in DNA content, due to deliberate or inadvertent mutations. Mutant progeny that have the same functionality as screened for in the originally transformed cell are included in the definition of progeny or as transformants. The cells can be prokaryotic or eukaryotic.

The term “oligonucleotide” as used herein is defined as a molecule comprised of two or more deoxyribonucleotides or ribonucleotides. The exact size will depend on many factors, which in turn depends on the ultimate function or use of the oligonucleotide. Oligonucleotides can be prepared by any suitable method, including, for example, cloning and restriction of appropriate sequences and direct chemical synthesis by a method such as the phosphotriester method of Narang et al., 1979, Meth. Enzymol. 68:90-99; the phosphodiester method of Brown et al., 1979, Meth. Enzymol. 68:109-151; the diethylphosphoramidite method of Beaucage et al., 1981, Tetrahedron Lett. 22:1859-1862; and the solid support method of U.S. Pat. No. 4,458,066, each incorporated herein by reference. A review of synthesis methods is provided in Goodchild, 1990, Bioconjugate Chemistry 1(3):165-187, incorporated herein by reference.

The term “primer” as used herein refers to an oligonucleotide capable of acting as a point of initiation of synthesis when placed under conditions in which primer extension is initiated. Synthesis of a primer extension product that is complementary to a nucleic acid strand is initiated in the presence of the requisite four different nucleoside triphosphates and a DNA polymerase in an appropriate buffer at a suitable temperature. A “buffer” includes a buffer, cofactors (such as divalent metal ions) and salt (to provide the appropriate ionic strength), adjusted to the desired pH.

A primer that hybridizes to the non-coding strand of a gene sequence (equivalently, is a subsequence of the noncoding strand) is referred to herein as an “upstream” or “forward” primer. A primer that hybridizes to the coding strand of a gene sequence is referred to herein as a “downstream” or “reverse” primer.

The term “protein” is used interchangeably here with the terms “peptide” and “polypeptide,” and refers to a molecule comprising two or more amino acid residues joined by a peptide bond. Families of amino acid residues having similar side chains have been defined in the art. These families include amino acids with basic side chains (e.g., lysine, arginine, histidine), acidic side chains (e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g., asparagine, glutamine, serine, threonine, tyrosine), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan, cysteine, glycine), beta-branched side chains (e.g., threonine, valine, isoleucine) and aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine). Standard three-letter or one-letter amino acid abbreviations are used herein. Equivalent substitutions may be included within the scope of the The peptides, polypeptides and proteins of the invention can comprise one or more non-classical amino acids. Non-classical amino acids include but are not limited to the D-isomers of the common amino acids, α-amino isobutyric acid, 4-aminobutyric acid (4-Abu), 2-aminobutyric acid (2-Abu), 6-amino hexanoic acid (Ahx), 2-amino isobutyric acid (2-Aib), 3-amino propionoic acid, ornithine, norleucine, norvaline, hydroxyproline, sarcosine, citrulline, cysteic acid, t-butylglycine, t-butylalanine, phenylglycine, cyclohexylalanine, β-alanine, fluoro-amino acids, designer amino acids such as β-methyl amino acids, Cα-methyl amino acids, Na-methyl amino acids and amino acid analogs in general.

The term “Ab” or “antibody” refers to polyclonal and monoclonal antibodies (MAb), chimeric antibodies, humanized antibodies, human antibodies, immunoglobulins or antibody or functional fragments of an antibody that bind to a target antigen. Examples of such functional entities include complete antibody molecules, antibody fragments, such as Fv, single chain Fv, complementarity determining regions (CDRs), V_(L) (light chain variable region), V_(H) (heavy chain variable region) and any combination of those or any other functional portion of an immunoglobulin peptide capable of binding to target antigen. Certain orders of portions are disclosed herein, but all orders are intended to be within the scope of the invention. For example, the TAB2.5 construct has the following order: vH-(GGGGS)₆-vL; however, the example is non-limiting, and all orders of vL and vH, are contemplated to be within the scope of the invention.

As used herein, the term “linker” shall refer to a sequence of amino acids that joins two fragments of a TAB molecule. The fragments may be joined in any order, as set forth herein. Linker length may vary. The length of the linker need not be 30 amino acids in length, as disclosed herein, and different linker lengths are contemplated to be within the scope of the invention (e.g., the TAB 2.4 molecule has a linker length of 15 amino acids, and the TAB2.5 and TAB2.8 molecules have a linker length of 30 amino acids).

As used herein, a “linking structure” shall refer to a structure, which links two drug moieties. With respect to a prodrug, for example, a linker may also join an active to inactive moiety, the inactive moiety being removed enzymatically or spontaneously, for example, after cleavage or removal of the inactive moiety [see, for example, Papot, S. Tranoy, I. Tillequin, Florent, J. C., Gesson, J. P. (2002) Design of selectively activated anticancer prodrugs: elimination and cyclization strategies Curr. Med. Chem. Anti-Canc Agents 2, 155-185].

The term “prodrug” refers to a compound that is converted via one or more enzymatically-catalyzed or physiologically-catalyzed steps into an active compound that has an increased pharmacological activity relative to the prodrug. A prodrug can comprise a propart, or inactive moiety, and an active drug part or detectable moiety. Optionally, the prodrug also contains a linking structure. For example, the prodrug can be cleaved by an enzyme to release an active drug. Alternatively, an enzyme could alter the prodrug to release a detectable moiety useful, for example, as a diagnostic. In a more specific example, prodrug cleavage by the targeted enzyme releases the active drug into the vicinity of the target bound to the targeted enzyme. “Pro-part” and “inactive moiety” refers to the inactive portion of the prodrug after it has been converted.

As used herein, “GC-MeI” shall refer to the prodrug glutaryl-cephalosporin-melphalan as disclosed, for example, in Senter et al., U.S. Pat. No. 5,773,435, which is incorporated by reference herein, including any drawings.

As used herein, “Mel” shall mean Melphalan. The structure of MeI is well known in the art and can also be found in U.S. Pat. No. 5,773,435, incorporated by reference herein including any drawings.

Prodrugs can be designed to release a variety of drugs, including doxorubicin, vinblastin, paclitaxel, duocarmycin, camptothecin, alkylating drugs, topoisomerase inhibitors, platinum compounds and other drugs. Of particular interest are prodrugs that can be activated by lactamases [see, for example, Senter, P. D., and Springer, C. J. (2001) Selective activation of anticancer prodrugs by monoclonal antibody-enzyme conjugates Adv Drug Deliv Res 53, 247-264]. Other examples of prodrugs activated by various enzymes are known [see, Bagshawe, K. D., Sharma, S. K., Burke, P. J., Melton, R. G. and Knox, J. (1999) Developments with targeted enzymes in cancer therapy; also see, Niculescu-Duvaz, I., Friedlos, D., Niculescu-Duvez, D., Davies L. and Springer, C. J. (1999) Prodrugs for antibody- and gene-directed enzyme prodrug therapies (ADEPT and GDEPT) Anticancer Drug Des 14, 517-538].

As used herein the language “pharmaceutically acceptable carrier” is intended to include any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like, compatible with pharmaceutical administration. The use of such media and agents for pharmaceutically active substances is well known in the art.

As used herein, “dosing interval” shall mean the interval between administration of the protein and subsequent administration of the pro-drug.

The term “% sequence homology” is used interchangeably herein with the terms “% homology,” “% sequence identity” and “% identity” and refers to the level of amino acid sequence identity between two or more peptide sequences, when aligned using a sequence alignment program. For example, as used herein, 80% homology means the same thing as 80% sequence identity determined by a defined algorithm, and accordingly, a homologue of a given sequence has greater than 80% sequence identity over a length of the given sequence. Exemplary levels of sequence identity include, but are not limited to, 60, 70, 80, 85, 90, 95, 98 or 99% or more sequence identity to a given sequence.

Exemplary computer programs that can be used to determine identity between two sequences include, but are not limited to, the suite of BLAST programs, e.g., BLASTN, BLASTX, and TBLASTX, BLASTP and TBLASTN, which are well-known to one skilled and the art. See also Altschul et al., 1990, J. Mol. Biol. 215: 403-10 and Altschul et al., 1997, Nucleic Acids Res., 25:3389-3402. Sequence searches are typically carried out using the BLASTP program when evaluating a given amino acid sequence relative to amino acid sequences in the GenBank Protein Sequences and other public databases. The BLASTX program is preferred for searching nucleic acid sequences that have been translated in all reading frames against amino acid sequences in the GenBank Protein Sequences and other public databases. Both BLASTP and BLASTX are run using default parameters of an open gap penalty of 11.0, and an extended gap penalty of 1.0, and utilize the BLOSUM-62 matrix. See Altschul, et al., 1997.

A preferred alignment of selected sequences in order to determine “% identity” between two or more sequences, is performed using for example, the CLUSTAL-W program in MacVector version 6.5, operated with default parameters, including an open gap penalty of 10.0, an extended gap penalty of 0.1, and a BLOSUM 30 similarity matrix.

The present invention relates to TAB molecules, ADEPT constructs directed against TAG-72, and their use in therapy, especially with prodrugs as described herein. The molecules of the current invention have been preferably deimmunized and do not elicit an immune response.

In a first aspect, the TAB molecule comprises an antibody/enzyme conjugate. In a preferred embodiment, the TAB molecule comprises an scFv, and the scFv has an unmodified amino acid sequence, the amino acid sequence comprising the sequence set forth in SEQ ID NO: 2. In a preferred embodiment, the TAB molecule has an amino acid sequence modified from the amino acid sequence set forth in SEQ ID NO: 2, the modification comprising at least one position selected from group consisting of: h8, h57, h62, h80, 15, 153, 179 and 1105, the h and 1 in front of each designated position denoting a heavy or light chain, respectively, wherein numbering is with respect to the scFv set forth in SEQ ID NO: 2, based on the Kabat system (see, for example, Wu, T. T. and E. A. Kabat (1970) J. Exp. Med. 132, 211-250). In a preferred embodiment, the TAB molecule is modified at the following positions: h80, 15, 153 and 179. In a preferred embodiment, the TAB molecule has the following modifications: hV80L, 1S5T, 1A53T and 1K79E. In a preferred embodiment, the TAB molecule comprises a TAB2.4, TAB2.5 or TAB2.8 molecule, the TAB2.4, TAB2.5 or TAB2.8 molecule comprising SEQ ID NO: 2, SEQ ID NO: 20 or SEQ ID NO: 22, respectively.

In a preferred embodiment, the TAB molecule further comprises an enzyme. In a preferred embodiment, the enzyme comprises a BLA. In a preferred embodiment, the BLA comprises TEM-4.

In a preferred embodiment, the TAB molecule comprises a full-length antibody/enzyme TAB conjugate, and the scFv has an unmodified amino acid sequence, the amino acid sequence comprising the sequence set forth in SEQ ID NO: 2. In a preferred embodiment, the TAB molecule has an amino acid sequence modified from the amino acid sequence set forth in SEQ ID NO: 8, the modification comprising at least one position selected from group consisting of: h8, h57, h62, h80, 15, 153, 179 and 1105, the h and 1 in front of each designated position denoting a heavy or light chain, respectively, wherein numbering is with respect to the scFv set forth in SEQ ID NO: 2, based on the Kabat system as set forth herein. In a preferred embodiment, the TAB molecule is modified at the following positions: h80, 15, 153 and 179. In a preferred embodiment, the TAB molecule has the following modifications: hV80L,1S5T,1A53T and 1K₇₉E. In a preferred embodiment, the TAB molecule comprises a TAB2.4, TAB2.5 or TAB2.8 molecule, the TAB2.4, TAB2.5 or TAB2.8 molecule comprising SEQ ID NO: 8, SEQ ID NO: 10 or TAB: 16, respectively.

In a preferred embodiment, the molecule comprises TAB2.6 having SEQ ID NO: 12. In a preferred embodiment, the molecule comprises clone ME374.4, ME375.18, ME374.31, ME374.63, ME374.73 or ME375.69.

In another embodiment, the TAB is a milieu-dependent targeted agent as described in PCT Application Number US03/18200, filed Jun. 12, 2002 and incorporated herein by reference in its entirety. TAB molecules of the present invention may be shown to preferentially bind to a target relative to a non-target under differing mileaus between the target and the non-target. The difference in binding can be caused by any difference between the target and non-target such as, for example, a difference in pH, oxygen pressure, concentration of solutes or analytes (e.g., lactic acid, sugars or other organic or inorganic molecules), temperature, light or ionic strength. Preferential binding of the TABs of the current invention can be used to bind to a target under a desired set of conditions, identify a target in vitro, ex vivo, in situ or in vivo (e.g., a target tissue in a subject), kill a target cell or tissue or convert a prodrug into an active drug in or near a target tissue.

In one embodiment, the TAB is selected, made or modified using an affinity maturation method, e.g., as described in PCT application US03/18187, with a priority date filed Jun. 12, 2002 and incorporated herein by reference in its entirety.

In another embodiment, the TAB is selected, made or modified using a loop-grafting method, e.g., as described in U.S. patent application Ser. No. 10/170,387, filed Jun. 12, 2002 and incorporated herein by reference in its entirety.

In another embodiment, the TAB is a multifunctional polypeptide, e.g., as described in U.S. patent application Ser. No. 10/170,729, filed Jun. 12, 2002 and incorporated herein by reference in its entirety.

In another embodiment, the TABs of the current invention are used for diagnostic or therapeutic applications such as those disclosed, for example, in U.S. Pat. No. 4,975,278, which is incorporated herein by reference in its entirety, as well as methods well-known in the art.

In one embodiment, the TAB molecule further comprises an active moiety. The active moiety can be any molecule, or a part of a molecule, that has an activity. The activity can be any activity. Examples of types of activities that the active moiety can have include, for example, a detectable activity, an enzymatic activity, a therapeutic activity, a diagnostic activity, a toxic activity or a binding activity. The active moiety can be a discrete part of the TAB, for example, an enzyme that is fused or conjugated to the binding moiety, or it can be an integral part of the TAB, for example, binding of the TAB to the target can activate or inhibit an activity of the target.

In another embodiment, the active moiety exhibits enzymatic activity, e.g., it is an enzyme or an active fragment or derivative of an enzyme. Of particular interest are enzymes that can be used to activate a prodrug in a therapeutic setting. A large number of enzymes with different catalytic modes of action have been used to activate prodrugs. See, e.g., Melton & Knox Enzyme-prodrug strategies for cancer therapy (1999) and Bagshawe et al., Curr Opin Immunol 11:579 (1999). Examples of types of enzymes that can be used to make the TABs of the present invention include, but are not limited to, proteases, carboxypeptidases, β-lactamases, asparaginases, oxidases, hydrolases, lyases, lipases, cellulases, amylases, aldolases, phosphatases, kinases, tranferases, polymerases, nucleases, nucleotidases, laccases, reductases, and the like. (See, e.g., co-pending U.S. patent application Ser. No. 09/954,385, filed Sep. 12, 2001, incorporated herein by reference in its entirety.) As such, TABs of the invention can, for example, exhibit protease, carboxypeptidase, β-lactamase, asparaginase, oxidase, hydrolase, lyase, lipase, cellulase, amylase, aldolase, phosphatase, kinase, tranferase, polymerase, nuclease, nucleotidase, laccase or reductase activity or the like. Examples of enzymes that can be used are those that can activate a prodrug, discussed below, and those that can produce a toxic agent from a metabolite, e.g., hydrogen peroxide from glucose. See Christofidou-Solomidou et al, 2000, Am J Physiol Lung Cell Mol Physiol 278:L794.

In one embodiment, the present invention provides a TAB further comprising a β-lactamase (“BLA”). A representative BLA sequence is depicted in FIG. 1.

BLA enzymes are widely distributed in both gram-negative and gram-positive bacteria. BLA sequences are well known. A representative example of a BLA sequence is depicted in SEQ ID NO: 4. BLA enzymes vary in specificity, but have in common that they hydrolyze β-lactams, producing substituted β-amino acids. Thus, they confer resistance to antibiotics containing β-lactams. Because BLA enzymes are not endogenous to mammals, they are subject to minimal interference from inhibitors, enzyme substrates, or endogenous enzyme systems (unlike proteases), and therefore are particularly well-suited for therapeutic administration. BLA enzymes are further well-suited to the therapeutic methods of the present invention because of their small size (BLA from E. cloacae is a monomer of 39 kD; BLA from E. coli is a monomer of 30 kD) and because they have a high specific activity against their substrates and have optimal activity at 37° C. See Melton et al., Enzyme-Prodrug Strategies for Cancer Therapy, Kluwer Academic/Plenum Publishers, New York (1999).

Examples of specific BLAs that can be used to make the TABs of the present invention include, but are not limited to, Class A, B, C or D β-lactamase, β-galactosidase, (see Benito et al., FEMS Microbiol. Lett. 123:107 (1994)), fibronectin, glucose oxidase, glutathione S-transferase, see Napolitano et al., Chem. Biol. 3:359 (1996) and tissue plasminogen activator, see Smith et al., J. Biol. Chem. 270:30486 (1995). The β-lactamases have been divided into four classes based on their sequences. See Thomson et al., 2000, Microbes and Infection 2:1225-35. The serine β-lactamases are subdivided into three classes: A (penicillinases), C (cephalosporinases) and D (oxacillnases). Class B β-lactamases are the zinc-containing or metallo β-lactamases. Any class of BLA can be utilized to generate a TAB of the invention.

In one embodiment, the BLA has a measurable specific activity. In one embodiment of the invention, the BLA has a specific activity greater than about 0.01 U/pmol against nitrocefin using the assay described in U.S. patent application Ser. No. 10/022,097. In another embodiment, the specific activity is greater than about 0.1 U/pmol. In another embodiment, the specific activity is greater than about 1 U/pmol. Preferably, these specific activities refer to the specific activity of the BLA when it is bound to a target.

In one embodiment, the BLA enzyme in the TAB comprises the amino acid sequence set forth in SEQ ID NO: 4. In another embodiment, the BLA enzyme in the TAB is at least 50%, 60%, 70%, 80%, 90%, 95%, 98% or 99% or more identical to the sequence depicted in SEQ ID NO: 4.

The targets bound by the TAB, or one or more binding moieties, can be any substance or composition to which a molecule can be made to bind to TAG-72. In one embodiment, the target is a surface. In one embodiment, the surface is a biological surface. In another embodiment, the biological surface is a surface of an organ. In another embodiment, the biological surface is a surface of a tissue. In another embodiment, the biological surface is a surface of a cell. In another embodiment, the biological surface is a surface of a diseased organ, tissue or cell. In another embodiment, the biological surface is a surface of a normal or healthy organ, tissue or cell. In another embodiment, the surface is a macromolecule in the interstitial space of a tissue. In another embodiment, the biological surface is the surface of a virus or pathogen. In another embodiment, the surface is a non-biological surface. In another embodiment, the non-biological surface is a surface of a medical device. In another embodiment, the medical device is a therapeutic device. In another embodiment, the therapeutic device is an implanted therapeutic device. In another embodiment, the medical device is a diagnostic device. In another embodiment, the diagnostic device is a well or tray.

Tissues are complex targets and refer to a single cell type, a collection of cell types or an aggregate of cells generally of a particular kind. Tissue may be intact or modified. General classes of tissue in humans include, but are not limited to, epithelial tissue, connective tissue, nerve tissue and muscle tissue.

In another embodiment, the target is a cancer-related target that expresses the antigen TAG-72 or that has TAG-72 bound to itself or that has TAG-72 located in its vicinity. The cancer-related target can be any target that a composition of the invention binds to as part of the diagnosis, detection or treatment of a cancer or cancer-associated condition in a subject, for example, a cancerous cell, tissue or organ, a molecule associated with a cancerous cell, tissue or organ, or a molecule, cell, tissue or organ that is associated with a cancerous cell, tissue or organ (e.g., a tumor-bound diagnostic or therapeutic molecule administered to a subject or to a biopsy taken from a subject, or a healthy tissue, such as vasculature, that is associated with cancerous tissue).

In a second aspect, the invention is drawn to a nucleic acid encoding a TAB conjugate as set forth in any of the embodiments of the first aspect, as well as those provided in the description, herein. In a preferred embodiment, the nucleic acid comprises at least one of the following sequences: SEQ ID NO: 7, SEQ ID NO: 9, SEQ ID NO: 15 or SEQ ID NO: 11. In a preferred embodiment, the nucleic acid comprises SEQ ID NO: 13.

The nucleic acid can be, for example, a DNA or an RNA. The present invention also provides a plasmid comprising a nucleic acid encoding a polypeptide comprising all or part of a TAB. The plasmid can be, for example, an expression plasmid that allows expression of the polypeptide in a host cell or organism, or in vitro. The expression vector can allow expression of the polypeptide in, for example, a bacterial cell. The bacterial cell can be, for example, an E. coli cell.

Because of the redundancy in the genetic code, typically a large number of DNA sequences encode any given amino acid sequence and are, in this sense, equivalent. As described below, it may be desirable to select one or another equivalent DNA sequences for use in an expression vector, based on the preferred codon usage of the host cell into which the expression vector will be inserted. The present invention is intended to encompass all DNA sequences that encode the desired TAB.

An operable expression clone may be used and is constructed by placing the coding sequence in operable linkage with a suitable control sequence in an expression vector. The vector can be designed to replicate autonomously in the host cell or to integrate into the chromosomal DNA of the host cell. The resulting clone is used to transform a suitable host, and the transformed host is cultured under conditions suitable for expression of the coding sequence. The expressed TAB is then isolated from the medium or from the cells, although recovery and purification of the TAB may not be necessary in some instances.

Construction of suitable clones containing the coding sequence and a suitable control sequence employ standard ligation and restriction techniques that are well understood in the art. In general, isolated plasmids, DNA sequences or synthesized oligonucleotides are cleaved, modified and religated in the form desired. Suitable restriction sites can, if not normally available, be added to the ends of the coding sequence so as to facilitate construction of an expression clone.

Site-specific DNA cleavage is performed by treating with a suitable restriction enzyme (or enzymes) under conditions that are generally understood in the art and specified by the manufacturers of commercially available restriction enzymes. See, e.g., product catalogs from Amersham (Arlington Heights, Ill.), Roche Molecular Biochemicals (Indianapolis, Ind.), and New England Biolabs (Beverly, Mass.). Incubation times of about one to two hours at a temperature that is optimal for the particular enzyme are typical. After each incubation, protein is removed by extraction with phenol and chloroform; this extraction can be followed by ether extraction and recovery of the DNA from aqueous fractions by precipitation with ethanol. If desired, size separation of the cleaved fragments may be performed by polyacrylamide gel or agarose gel electrophoresis using standard techniques. See, e.g., Maxam et al., 1980, Methods in Enzymology 65:499-560.

Ligations can be performed, for example, in 15-30 μl volumes under the following standard conditions and temperatures: 20 mM Tris-Cl, pH 7.5, 10 mM MgCl₂, 10 mM DTT, 33 μg/ml BSA, 10-50 mM NaCl, and either 40 μM ATP and 0.01-0.02 (Weiss) units T4 DNA ligase at 0° C. (for ligation of fragments with complementary single-stranded ends) or 1 mM ATP and 0.3-0.6 units T4 DNA ligase at 14° C. (for “blunt end” ligation). Intermolecular ligations of fragments with complementary ends are usually performed at 33-100 μg/ml total DNA concentrations (5-100 nM total ends concentration). Intermolecular blunt end ligations (usually employing a 20-30 fold molar excess of linkers, optionally) are performed at 1 μM total ends concentration.

Correct ligations for plasmid construction can be confirmed using any suitable method known in the art. For example, correct ligations for plasmid construction can be confirmed by first transforming a suitable host, such as E. coli strain DG101 (ATCC 47043) or E. coli strain DG116 (ATCC 53606), with the ligation mixture. Successful transformants are selected by ampicillin, tetracycline or other antibiotic resistance or sensitivity or by using other markers, depending on the mode of plasmid construction, as is understood in the art. Plasmids from the transformants are then prepared according to the method of Clewell et al., 1969, Proc. Natl. Acad. Sci. USA 62:1159, optionally following chloramphenicol amplification. See Clewell, 1972, J. Bacteriol. 110:667. Alternatively, plasmid DNA can be prepared using the “Base-Acid” extraction method at page 11 of the Bethesda Research Laboratories publication Focus 5 (2), and very pure plasmid DNA can be obtained by replacing steps 12 through 17 of the protocol with CsCl/ethidium bromide ultracentrifugation of the DNA. As another alternative, a commercially available plasmid DNA isolation kit, e.g., HISPEED™, QIAFILTER™ and QIAGEN® plasmid DNA isolation kits (Qiagen, Valencia Calif.) can be employed following the protocols supplied by the vendor. The isolated DNA can be analyzed by, for example, restriction enzyme digestion and/or sequenced by the dideoxy method of Sanger et al., 1977, Proc. Natl. Acad. Sci. USA 74:5463, as further described by Messing et al., 1981, Nuc. Acids Res. 9:309, or by the method of Maxam et al., 1980, Methods in Enzymology 65:499.

The control sequences, expression vectors and transformation methods are dependent on the type of host cell used to express the gene. Generally, prokaryotic, yeast, insect or mammalian cells are used as hosts. Prokaryotic hosts are in general the most efficient and convenient for the production of recombinant proteins and are therefore preferred for the expression of the protein.

The prokaryote most frequently used to express recombinant proteins is E. coli. However, microbial strains other than E. coli can also be used, such as bacilli, for example Bacillus subtilis, various species of Pseudomonas and Salmonella, and other bacterial strains. In such prokaryotic systems, plasmid vectors that contain replication sites and control sequences derived from the host or a species compatible with the host are typically used.

For expression of constructions under control of most bacterial promoters, E. coli K12 strain MM294, obtained from the E. coli Genetic Stock Center under GCSC #6135, can be used as the host. For expression vectors with the P_(L)N_(RBS) or P_(L) T7_(RBS) control sequence, E. coli K12 strain MC1000 lambda lysogen, N₇N₅₃cI857 SusP₈₀, ATCC 39531, may be used. E. coli DG116, which was deposited with the ATCC (ATCC 53606) on Apr. 7, 1987, and E. coli KB2, which was deposited with the ATCC (ATCC 53075) on Mar. 29, 1985, are also useful host cells. For M13 phage recombinants, E. coli strains susceptible to phage infection, such as E. coli K12 strain DG98 (ATCC 39768), are employed. The DG98 strain was deposited with the ATCC on Jul. 13, 1984.

E. coli is typically transformed using derivatives of pBR322, described by Bolivar et al., 1977, Gene 2:95. Plasmid pBR322 contains genes for ampicillin and tetracycline resistance. These drug resistance markers can be either retained or destroyed in constructing the desired vector and so help to detect the presence of a desired recombinant. Commonly used prokaryotic control sequences, i.e., a promoter for transcription initiation, optionally with an operator, along with a ribosome binding site sequence, include the β-lactamase (penicillinase) and lactose (lac) promoter systems, see Chang et al., 1977, Nature 198:1056, the tryptophan (trp) promoter system, see Goeddel et al., 1980, Nuc. Acids Res. 8:4057, and the lambda-derived P_(L) promoter, see Shimatake et al., 1981, Nature 292:128, and gene N ribosome binding site (N_(RBS)). A portable control system cassette is set forth in U.S. Pat. No. 4,711,845, issued Dec. 8, 1987. This cassette comprises a P_(L) promoter operably linked to the N RBS in turn positioned upstream of a third DNA sequence having at least one restriction site that permits cleavage within six base pairs 3′ of the N_(RBS) sequence. Also useful is the phosphatase A (phoA) system described by Chang et al., in European Patent Publication No. 196,864, published Oct. 8, 1986. However, any available promoter system compatible with prokaryotes can be used to construct an expression vector of the invention.

In addition to bacteria, eukaryotic microbes, such as yeast, can also be used as recombinant host cells. Laboratory strains of Saccharomyces cerevisiae, Baker's yeast, are most often used, although a number of other strains are commonly available. While vectors employing the two micron origin of replication are common, see Broach, 1983, Meth. Enz. 101:307, other plasmid vectors suitable for yeast expression are known. See, e.g., Stinchcomb et al., 1979, Nature 282:39; Tschempe et al., 1980, Gene 10:157; and Clarke et al., 1983, Meth. Enz. 101:300. Control sequences for yeast vectors include promoters for the synthesis of glycolytic enzymes. See Hess et al., 1968, J. Adv. Enzyme Reg. 7:149; Holland et al., 1978, Biotechnology 17:4900; and Holland et al., 1981, J. Biol. Chem. 256:1385. Additional promoters known in the art include the promoter for 3-phosphoglycerate kinase, see Hitzeman et al., 1980, J. Biol. Chem. 255:2073, and those for other glycolytic enzymes, such as glyceraldehyde 3-phosphate dehydrogenase, hexokinase, pyruvate decarboxylase, phosphofructokinase, glucose-6-phosphate isomerase, 3-phosphoglycerate mutase, pyruvate kinase, triosephosphate isomerase, phosphoglucose isomerase and glucokinase. Other promoters that have the additional advantage of transcription controlled by growth conditions are the promoter regions for alcohol dehydrogenase 2, isocytochrome C, acid phosphatase, degradative enzymes associated with nitrogen metabolism and enzymes responsible for maltose and galactose utilization.

Terminator sequences may also be used to enhance expression when placed at the 3′ end of the coding sequence. Such terminators are found in the 3′ untranslated region following the coding sequences in yeast-derived genes. Any vector containing a yeast-compatible promoter, origin of replication and other control sequences is suitable for use in constructing yeast expression vectors.

The coding sequence can also be expressed in eukaryotic host cell cultures derived from multicellular organisms. See, e.g., Tissue Culture, Academic Press, Cruz and Patterson, editors (1973). Useful host cell lines include COS-7, COS-A2, CV-1, murine cells such as murine myelomas N51 and VERO, HeLa cells and Chinese hamster ovary (CHO) cells. Expression vectors for such cells ordinarily include promoters and control sequences compatible with mammalian cells such as, for example, the commonly used early and late promoters from Simian Virus 40 (SV 40), see Fiers et al., 1978, Nature 273:113, or other viral promoters such as those derived from polyoma, adenovirus 2, bovine papilloma virus (BPV) or avian sarcoma viruses, or immunoglobulin promoters and heat shock promoters.

Enhancer regions are also important in optimizing expression; these are, generally, sequences found upstream of the promoter region. Origins of replication may be obtained, if needed, from viral sources. However, integration into the chromosome is a common mechanism for DNA replication in eukaryotes.

Plant cells can also be used as hosts, and control sequences compatible with plant cells, such as the nopaline synthase promoter and polyadenylation signal sequences, see Depicker et al., 1982, J. Mol. Appl. Gen. 1:561, are available. Expression systems employing insect cells utilizing the control systems provided by baculovirus vectors have also been described. See Miller et al., in Genetic Engineering (1986), Setlow et al., eds., Plenum Publishing, Vol. 8, pp. 277-97. Insect cell-based expression can be accomplished in Spodoptera frugipeida. These systems are also successful in producing recombinant enzymes.

Depending on the host cell used, transformation is done using standard techniques appropriate to such cells. The calcium treatment employing calcium chloride, as described by Cohen, 1972, Proc. Natl. Acad. Sci. USA 69:2110, is used for prokaryotes or other cells that contain substantial cell wall barriers. Infection with Agrobacterium tumefaciens, see Shaw et al., 1983, Gene 23:315, is used for certain plant cells. For mammalian cells, the calcium phosphate precipitation method of Graham et al., 1978, Virology 52:546 is preferred. Transformations into yeast are carried out according to the method of Van Solingen et al., 1977, J. Bact. 130:946, and Hsiao et al., 1979, Proc. Natl. Acad. Sci. USA 76:3829.

It may be desirable to modify the sequence of a DNA encoding a polypeptide comprising all or part of a TAB of the invention to provide, for example, a sequence more compatible with the codon usage of the host cell without modifying the amino acid sequence of the encoded protein. Such modifications to the initial 5-6 codons may improve expression efficiency. DNA sequences which have been modified to improve expression efficiency, but which encode the same amino acid sequence, are considered to be equivalent and encompassed by the present invention.

A variety of site-specific primer-directed mutagenesis methods are available and well-known in the art. See, e.g., Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, 1989, second edition, chapter 15.51, “Oligonucleotide-mediated mutagenesis,” which is incorporated herein by reference. The polymerase chain reaction (PCR) can be used to perform site-specific mutagenesis. In another technique now standard in the art, a synthetic oligonucleotide encoding the desired mutation is used as a primer to direct synthesis of a complementary nucleic acid sequence contained in a single-stranded vector, such as pBSM13+ derivatives, that serves as a template for construction of the extension product of the mutagenizing primer. The mutagenized DNA is transformed into a host bacterium, and cultures of the transformed bacteria are plated and identified. The identification of modified vectors may involve transfer of the DNA of selected transformants to a nitrocellulose filter or other membrane and the “lifts” hybridized with kinased synthetic mutagenic primer at a temperature that permits hybridization of an exact match to the modified sequence but prevents hybridization with the original unmutagenized strand. Transformants that contain DNA that hybridizes with the probe are then cultured (the sequence of the DNA is generally confirmed by sequence analysis) and serve as a reservoir of the modified DNA.

Once the polypeptide has been expressed in a recombinant host cell, purification of the polypeptide may be desired. A variety of purification procedures can be used, such as those set forth in the Examples. Proteins can be purified by various chromatography methods like ion exchange chromatography, size exclusion chromatography, hydrophobic interaction chromatography and related techniques. In addition, proteins can be purified by precipitation of either the protein of interest itself or by selective precipitation of contaminating products using salts or other reagents that affect solubility. Proteins can also be purified by extraction.

In one embodiment, a nucleic acid encoding the TAB hybridizes to a nucleic acid complementary to a nucleic acid encoding any of the amino acid sequences disclosed herein under highly stringent conditions. The highly stringent conditions can be, for example, hybridization to filter-bound DNA in 0.5 M NaHPO₄, 7% sodium dodecyl sulfate (SDS), 1 mM EDTA at 65° C. and washing in 0.1×SSC/0.1% SDS at 68° C. (Ausubel et al., eds., 1989, Current Protocols in Molecular Biology, Vol. I, Green Publishing Associates, Inc., and John Wiley & Sons, Inc., New York, at p. 2.10.3). Other highly stringent conditions can be found in, for example, Current Protocols in Molecular Biology, at pages 2.10.1-16 and Molecular Cloning: A Laboratory Manual, 2d ed., Sambrook et al. (eds.), Cold Spring Harbor Laboratory Press, 1989, pages 9.47-57). In another embodiment, moderately stringent conditions are used. The moderately stringent conditions can be, for example, washing in 0.2×SSC/0.1% SDS at 42° C. (Ausubel et al., 1989, supra). Other moderately stringent conditions can be found in, for example, Current Protocols in Molecular Biology, Vol. I, Ausubel et al. (eds.), Green Publishing Associates, Inc., and John Wiley & Sons, Inc., 1989, pages 2.10.1-16 and Molecular Cloning: A Laboratory Manual, 2d ed., Sambrook et al. (eds.), Cold Spring Harbor Laboratory Press, 1989, pages 9.47-57.

In a third aspect the present invention provides a method of treating a subject in need thereof comprising administering to a subject a TAB and a prodrug that is a substrate of the TAB. In another embodiment, the invention provides a method of treating a subject by administering to the subject a TAB molecule and a prodrug that is converted by the BLA into an active drug. In another embodiment, the TAB is specifically TAB2.4, TAB2.5 or TAB2.8 as set forth in SEQ ID NO: 8, SEQ ID NO: 10 or SEQ ID NO: 16, respectively.

Melphalan derivatives are especially suitable as the prodrug for this embodiment of the invention. Examples of enzyme/prodrug/active drug combinations can be found in, e.g., Senter et al., U.S. Pat. No. 5,773,435, which is incorporated by reference herein, including any drawings. Other examples of suitable prodrugs for this embodiment are provided in, e.g., Melton et al., Enzyme-Prodrug Strategies for Cancer Therapy, Kluwer Academic/Plenum Publishers, New York (1999), Bagshawe et al., Current Opinion in Immunology 11:579-83 (1999) and Kerr et al., Bioconjugate Chem. 9:255-59 (1998). Wilman, “Prodrugs In Cancer Chemotherapy,” Biochemical Society Transactions, 14, pp. 375-82 (615th Meeting, Belfast 1986) and V. J. Stella et al., “Prodrugs: A Chemical Approach To Targeted Drug Delivery,” Directed Drug Delivery, R. Borchardt et al. (ed), pp. 247-67 (Humana Press 1985).

The prodrugs of the invention can include, but are not limited to, auristatins, camptothecins, phosphate-containing prodrugs, thiophosphate-containing prodrugs, sulfate-containing prodrugs, peptide-containing prodrugs, D-amino acid-modified prodrugs, glycosylated prodrugs, β-lactam-containing prodrugs, optionally substituted phenoxyacetamide-containing prodrugs or optionally substituted phenylacetamide containing prodrugs, 5-fluorocytosine and other 5-fluorouridine prodrugs which can be converted by the enzyme of the conjugate into the more active cytotoxic free drug. Examples of cytotoxic drugs that can be derivatized into a prodrug form for use in this invention include, but are not limited to, etoposide, temposide, adriamycin, daunomycin, caminomycin, aminopterin, dactinomycin, mitomycins, cis-platinum and cis-platinum analogues, bleomycins, esperamicins (see U.S. Pat. No. 4,675,187), 5-fluorouracil, melphalan, other related nitrogen mustards and derivatives thereof. (See, e.g., U.S. Pat. No. 4,975,278).

In one embodiment of the invention, the TAB comprises an alkaline phosphatase (AP) that converts a 4′-phosphate derivative of the epipodophyl-lotoxin glucosides into an active anti-cancer drug. Such derivatives include etoposide-4′-phosphate, etoposide-4′-thiophosphate and teniposide-4′-phosphate. Other embodiments of the invention may include phosphate derivatives of these glucosides wherein the phosphate moiety is placed at other hydroxyl groups on the glucosides. According to another embodiment, however, the phosphate derivative used as a pro-drug in this invention is etoposide-4′-phosphate or etoposide-4′-thiophosphate. The targeted AP removes the phosphate group from the prodrug, releasing an active antitumor agent. The mitomycin phosphate prodrug of this embodiment may be an N⁷-C₁₋₈ alkyl phosphate derivative of mitomycin C or porfiromycin or pharmaceutically acceptable salts thereof. N⁷ refers to the nitrogen atom attached to the 7-position of the mitosane nucleus of the parent drug. According to another embodiment, the derivative used is 7-(2′-aminoethylphosphate)mitomycin (“MOP”). Alternatively, the MOP compound may be termed, 9-methoxy-7-[[(phos-phonooxy]ethyl]amino]mitosane disodium salt. Other embodiments of the invention may include the use pf N⁷-alkyl mitomycin phosphorothioates as prodrugs.

In still another embodiment of the invention, the TAB comprises a penicillin amidase enzyme that converts a novel adriamycin prodrug into the active antitumor drug adriamycin. In another embodiment, the penicillin amidase is a penicillin V amidase (“PVA”) isolated from Fusarium oxysporum that hydrolyzes phenoxyacetyl amide bonds. The prodrug utilized can be N-(p-hydroxyphenoxyacetyl)adriamycin (“APO”), which is hydrolyzed by the amidase to release the potent antitumor agent or adriamycin.

The present invention also comprises, for example, the use of the adriamycin prodrug, N-(p-hydroxyphenoxyacetyl)adriamycin and other related adriamycin prodrugs that can be derivatized in substantially the same manner. For example, use of the prodrug N-(phenoxyacetyl) adriamycin is also within the scope of the invention. In addition, it is to be understood that the adriamycin prodrugs of this invention include other N-hydroxyphenoxyacetyl derivatives of adriamycin, e.g., substituted at different positions of the phenyl ring, as well as N-phenoxyacetyl derivatives containing substituents on the phenyl ring other than the hydroxyl group described herein.

Furthermore, the present embodiment encompasses the use of other amidases, such as penicillin G amidase, as part of TAB as well as other prodrugs correspondingly derivatized such that the particular amidase can hydrolyze that prodrug to an active antitumor form. For example, when the TAB further comprises penicillin G amidase, the prodrug should contain a phenylacetylamide group (as opposed to the phenoxyacetylamide group of APO) because penicillin G amidases hydrolyze this type of amide bond (see, e.g., A. L. Margolin et al., Biochim. Biophys Acta. 616, pp. 283-89 (1980)). Thus, other prodrugs of the invention include N-(p-hydroxyphenylacetyl) adriamycin, N-(phenylacetyl) adriamycin and other optionally substituted N-phenylacetyl derivatives of adriamycin.

It should also be understood that the present invention includes any prodrug derived by reacting the amine group of the parent drug with the carboxyl group of phenoxyacetic acid, phenylacetic acid or other related acids. Thus, prodrugs of anthracyclines other than adriamycin that are capable of being derivatized and acting in substantially the same manner as the adriamycin prodrugs described herein falls within the scope of this invention. For example, other prodrugs that can be produced and used in accordance with this invention include hydroxyphenoxyacetylamide derivatives, hydroxyphenylacetylamide derivatives, phenoxyacetylamide derivatives and phenylacetylamide derivatives of anthracyclines such as daunomycin and caminomycin. Other amine-containing drugs such as melphalan, mitomycin, aminopterin, bleomycin and dactinomycin can also be modified described herein to yield prodrugs of the invention.

Another embodiment of the invention involves a TAB form of the enzyme cytosine deaminase (“CD”). The deaminase enzyme catalyzes the conversion of 5-fluorocytosine (“5-FC”), a compound lacking in antineoplastic activity, to the potent antitumor drug, 5-fluorouracil (“5-FU”).

In one embodiment, the prodrug is a peptide. Examples of peptides as prodrugs can be found in Trouet et al., Proc Natl Acad Sci USA 79:626 (1982), and Umemoto et al., Int J Cancer 43:677 (1989). These and other reports show that peptides are sufficiently stable in blood. Another advantage of peptide-derived prodrugs is their amino acid sequences can be chosen to confer suitable pharmacological properties like half-life, tissue distribution and low toxicity to the active drugs. Most reports of peptide-derived prodrugs relied on relatively nonspecific activation of the prodrug by, for instance, lysosomal enzymes.

The prodrug can be one that is converted to an active drug in more than one step. For example, the prodrug can be converted to a precursor of an active drug by the TAB. The precursor can be converted into the active drug by, for example, the catalytic activity of one or more additional TABs, the catalytic activities of one or more other enzymes administered to the subject, the catalytic activity of one or more enzymes naturally present in the subject or at the target site in the subject (e.g., a protease, a phosphatase, a kinase or a polymerase), by a drug that is administered to the subject or by a chemical process that is not enzymatically catalyzed (e.g., oxidation, hydrolysis, isomerization or epimerization).

Most studies involving prodrugs are generated after programs with existing drugs are found to be problematic. In particular anticancer drugs were generally characterized by a very low therapeutic index. By converting these drugs into prodrugs with reduced toxicity and then selectively activating them in the diseased tissue, the therapeutic index of the drug can be significantly increased. See, e.g., Melton et al., Enzyme-prodrug strategies for cancer therapy (1999), and Niculescu-Duvaz et al., Anticancer Drug Des 14:517 (1999).

The literature describes many methods to alter the substrate specificity of enzymes by protein engineering or directed evolution. Thus one skilled in the art is able to evolve the specificity of an enzyme to accommodate even structures that would be poor substrates for naturally-occurring enzymes. Accordingly, prodrugs can be designed even though the drugs were otherwise not amenable to a prodrug strategy.

Another embodiment of the method of this invention provides a method of combination chemotherapy using several prodrugs and a single TAB. According to this embodiment, a number of prodrugs are used that are all substrates for the same TAB. Thus, a particular TAB converts a number of prodrugs into cytotoxic form, resulting in increased antitumor activity at the tumor site.

There is often a requirement for extending the blood circulation half-lives of pharmaceutical peptides, proteins, or small molecules. Typically short half-lives—lasting minutes to hours—require not only frequent, but also high doses for therapeutic effect—often so high that initial peak doses cause side effects. Extending the half-life of such therapeutics permits lower, less frequent, and therefore potentially safer doses, which are cheaper to produce. Previously, researchers have increased protein half-life by fusing them covalently to PEG, see U.S. Pat. No. 5,711,944, human blood serum albumin, see U.S. Pat. No. 5,766,883, or Fc fragments, see WO 00/24782. In addition, nonspecific targeting of drugs to human serum albumin has been accomplished by chemical coupling drugs in vivo. (See U.S. Pat. No. 5,843,440). Furthermore, in the case of cancer drugs it has been proposed that high molecular weight drugs may localize in tumors due to enhanced permeability and retention. Therefore, improvement in the therapeutic index of a drug can be obtained by linking the drug to a protein or other high molecular weight polymer.

In one embodiment, the subject in need thereof is a cancer patient. In another embodiment, the TAB is targeted to a TAG-72 expressing cell, tissue, tumor or organ. In another embodiment, the prodrug is converted by the TAB into an active drug. In another embodiment, the active drug is an alkylating agent. In another embodiment, the prodrug is an anticancer nitrogen mustard prodrug. In another embodiment, the active drug is melphalan. In another embodiment, the prodrug is C-MeI. In another embodiment, the prodrug is glutaryl-C-MeI or glutaryl-C-MeI-L-Phe-NH2 (see, for example, Senter et al, U.S. Pat. No. 5,773,435, which is incorporated by reference herein, including any drawings and Kerr et al., Bioconjugate Chem. 9:255-59 (1998)). In another embodiment, the prodrug is vinca-cephalosporin or doxorubicin cephalosporin. See Bagshawe et al., Current Opinion in Immunology, 11:579-83 (1999). Other prodrug/enzyme combinations that can be used in the present invention include, but are not limited to, those found in U.S. Pat. No. 4,975,278 and Melton et al., Enzyme-Prodrug Strategies for Cancer Therapy Kluwer Academic/Plenum Publishers, New York (1999).

In a fourth aspect, the invention is drawn to a pharmaceutical composition comprising a TAB molecule. The TABs, nucleic acids encoding them and, in certain embodiments, prodrugs described herein can be incorporated into pharmaceutical compositions suitable for administration. Such compositions typically comprise the active compound and a pharmaceutically acceptable carrier. Except insofar as any conventional media or agent is incompatible with the active compound, use thereof in the compositions is contemplated. Supplementary active compounds can also be incorporated into the compositions.

The invention includes methods for preparing pharmaceutical compositions for modulating the expression or activity of a TAB, prodrug or nucleic acid of interest. Such methods comprise formulating a pharmaceutically acceptable carrier with an agent that modulates expression or activity of an active compound of interest. Such compositions can further include additional active agents. Thus, the invention further includes methods for preparing a pharmaceutical composition by formulating a pharmaceutically acceptable carrier with an agent that modulates expression or activity of a TAB, prodrug or nucleic acid of interest and one or more additional active compounds.

A pharmaceutical composition of the invention is formulated to be compatible with its intended route of administration. Examples of routes of administration include parenteral, e.g., intravenous, intradermal, subcutaneous, oral (e.g., inhalation), transdermal (topical), transmucosal and rectal administration. Solutions or suspensions used for parenteral, intradermal, or subcutaneous application can include the following components: a sterile diluent such as water for injection, saline solution, fixed oils, polyethylene glycols, glycerine, propylene glycol or other synthetic solvents; antibacterial agents such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. pH can be adjusted with acids or bases, such as hydrochloric acid or sodium hydroxide. The parenteral preparation can be enclosed in ampoules, disposable syringes or multiple dose vials made of glass or plastic.

Pharmaceutical compositions suitable for injectable use include sterile aqueous solutions (where water soluble) or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersions. For intravenous administration, suitable carriers include normal saline, Water for Injection, 5% dextrose or phosphate buffered saline (PBS). In all cases, the composition must be sterile and should be fluid to the extent that easy syringability exists. It must be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms such as bacteria and fungi. The carrier can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyethylene glycol, and the like) and suitable mixtures thereof. The proper fluidity can be maintained by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. Prevention of the action of microorganisms can be achieved by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, ascorbic acid, thimerosal and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars, polyalcohols such as mannitol, sorbitol, sodium chloride in the composition.

Sterile injectable solutions can be prepared by incorporating the active compound in the required amount in an appropriate solvent with one or a combination of ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the active compound into a sterile vehicle that contains a basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred method of preparation is freeze-drying which yields a powder of the active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof.

Oral compositions generally include an inert diluent or an edible carrier. They can be enclosed in gelatin capsules or compressed into tablets. For the purpose of oral therapeutic administration, the active compound can be incorporated with excipients and used in the form of tablets, troches or capsules.

Pharmaceutically compatible binding agents, and/or adjuvant materials can be included as part of the composition. The tablets, pills, capsules, troches and the like can contain any of the following ingredients, or compounds of a similar nature: a binder such as microcrystalline cellulose, gum tragacanth or gelatin; an excipient such as starch or lactose, a disintegrating agent such as alginic acid, Primogel, or corn starch; a lubricant such as magnesium stearate or Sterotes; a glidant such as colloidal silicon dioxide; a sweetening agent such as sucrose or saccharin; or a flavoring agent such as peppermint, methyl salicylate or orange flavoring.

For administration by inhalation, the compounds are delivered in the form of an aerosol spray from a pressurized container or dispenser that contains a suitable propellant, e.g., a gas such as carbon dioxide or a nebulizer.

Systemic administration can also be by transmucosal or transdermal means. For transmucosal or transdermal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art, and include, for example, for transmucosal administration, detergents, bile salts and fusidic acid derivatives. Transmucosal administration can be accomplished through the use of nasal sprays or suppositories. For transdermal administration, the active compounds are formulated into ointments, salves, gels or creams as generally known in the art.

The compounds can also be prepared in the form of suppositories (e.g., with conventional suppository bases such as cocoa butter and other glycerides) or retention enemas for rectal delivery.

In one embodiment, the active compounds are prepared with carriers that will protect the compound against rapid elimination from the body, such as a controlled release formulation, including implants and microencapsulated delivery systems. Biodegradable, biocompatible polymers can be used, such as ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters and polylactic acid. Methods for preparation of such formulations will be apparent to those skilled in the art. The materials can also be obtained commercially from Alza Corporation and Nova Pharmaceuticals, Inc. Liposomal suspensions (including liposomes targeted to infected cells with monoclonal antibodies to viral antigens) can also be used as pharmaceutically acceptable carriers. These can be prepared according to methods known to those skilled in the art, for example, as described in U.S. Pat. No. 4,522,811.

In one embodiment, the formulation comprises sulfobutylether-7-beta-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin, as disclosed, for example, in U.S. Pat. No. 6,216,375 and U.S. Pat. No. 6,537,988, each of which are incorporated by reference, herein, including any drawings.

Typically, the amount of TAB to be delivered to a subject will depend on a number of factors, including, for example, the route of administration, the activity of the TAB, the degree to which it is specifically targeted to the desired cells, tissues or organs of the subject, the length of time required to clear the non-specifically bound TAB from the subject, the desired therapeutic effect, the body mass of the subject, the age of the subject, the general health of the subject, the sex of the subject, the diet of the subject, the subject's immune response to the TAB, other medications or treatments being administered to the subject, the severity of the disease and the previous or future anticipated course of treatment.

For applications in which a prodrug also is administered, other factors affecting the determination of a therapeutically effective dose will include, for example, the amount of prodrug administered, the interval between administration of the TAB and the prodrug, the activity of the prodrug and its corresponding active drug and the side effects or toxicities of the prodrug and the active drug.

Examples of ranges of mass of TAB/mass of subject include, for example, from about 0.001 to 30 mg/kg body weight, from about 0.01 to 25 mg/kg body weight, from about 0.1 to 20 mg/kg body weight, and from about 1 to 10 mg/kg, 2 to 9 mg/kg, 3 to 8 mg/kg, 4 to 7 mg/kg, or 5 to 6 mg/kg body weight.

In a particular example, a subject is treated with a TAB in the range of between about 0.1 to 20 mg/kg body weight, one time per week for between about 1 to 10 weeks, preferably between 2 to 8 weeks, preferably between about 3 to 7 weeks and preferably for about 4, 5 or 6 weeks. It will also be appreciated that the effective dosage of TAB may increase or decrease over the course of a particular treatment, and that the treatment will continue, with or without modification, until a desired result is achieved or until the treatment is discontinued for another reason. Changes in dosage may result and become apparent from the results of diagnostic assays as described herein.

It is understood that appropriate doses of prodrugs depend upon a number of factors within the ken of the ordinarily skilled physician, veterinarian or researcher. The dose(s) of the prodrug will depend, for example, on the same factors provided above as factors affecting the effective dose of the TAB. Exemplary doses include milligram or microgram amounts of the prodrug per kilogram of subject or sample weight (e.g., about 1 microgram per kilogram to about 500 milligrams per kilogram, about 100 micrograms per kilogram to about 5 milligrams per kilogram or about 1 microgram per kilogram to about 50 micrograms per kilogram). It is furthermore understood that appropriate doses of a prodrug depend upon the potency of the prodrug with respect to the desired therapeutic effect. When one or more of these prodrugs is to be administered to an animal (e.g., a human), a physician, veterinarian or researcher may, for example, prescribe a relatively low dose at first, subsequently increasing the dose until an appropriate response is obtained.

Preferably, the TAB is administered to the subject, then the prodrug is administered. More preferably, the time between the administration of the TAB and administration of the prodrug is sufficient to allow the TAB to accumulate at its target site by binding to its target, and to allow unbound TAB to be cleared from the non-targeted portions of the subject's body. Most preferably, the ratio of target-bound TAB to unbound TAB in the subject's body will be at or near its maximum when the prodrug is administered. The time necessary after administration of the TAB to reach this point is called the clearing time. The clearing time can be determined or approximated in an experimental system by, for example, administering a detectable TAB (e.g., a radiolabeled or fluorescently labeled TAB) to a subject and simultaneously measuring the amount of enzyme at the target site and at a non-targeted control site at timed intervals. For some prodrugs, particularly those whose counterpart active drugs are highly toxic, it may be more important to ensure that the levels of unbound TAB in the subject's system are below a certain threshold. This too can be determined experimentally, as described above. Dosing intervals of between about 72 and about 96 hours are preferred.

In one embodiment, administration of the prodrug is systemic. In another embodiment, administration of the prodrug is at or near the target.

The pharmaceutical compositions can be included in a container, pack, dispenser or kit together with instructions for administration.

EXAMPLES Example 1 Construction of Plasmid pNA22.7 Expressing TAB2.1 Protein

The amino acid sequence of the scFv portion of TAB2.1 molecule was derived from murine anti-TAG-72 monoclonal antibody (mAb) CC49 sequence (Abergel et. al. (1993) Proteins: Structure, Function and Genetics 17:438-443). The nucleotide sequence of the synthetic gene was designed based on E. coli codon usage plus a 15-aa peptide linker connecting the vH and vL domains with the following genetic configuration: vH-(GGGGS)₃-vL. A 973-bp DNA fragment containing the designed gene was synthesized by McLab (South San Francisco, Calif.) with flanking BglI and EcoRV restriction enzyme sites and cloned into plasmid pPCRII-TOPO (Invitrogen Corp., Carlsbad, Calif.) resulting in plasmid pAG.

Plasmid pME25.1 was used to clone the synthetic scFv portion of CC49 antibody from plasmid pAG. Upon digestion of plasmids pAG and pME25.1 with BglI and EcoRV enzymes, a 0.88-kb insert fragment and a 4.3-kb vector fragment, respectively, were gel purified. They were then ligated, followed by transformation into E. coli TOP10 (Invitrogen, Carlsbad, Calif.) chemically competent cells and selection on LA+Cm5+0.1 CTX plates. Plasmid DNAs isolated from 10 transformants were checked for proper size and orientation of the CC49 scFv fragment by digestion with PvuII enzyme. Expected restriction patterns were observed for all 10 clones tested. After testing several of them for expression and binding, plasmid pNA22.7 was selected for further engineering and named TAB2.1.

Example 2 Construction of Plasmid pSW239.1 Expressing TAB2.4 Protein

Plasmid pSW239.1 (TAB2.4) was constructed using plasmid pNA22.7 (TAB2.1) as a PCR template by a modification of the regular Quikchange Mutagenesis protocol (Stratagene, CA) as described before (Wang, W. & Malcolm, B. A. BioTechniques 26:680-682 (1999)). This manipulation increases the linker size between vH and vL domains from 15-aa [(GGGGS)₃] to 30-aa [(GGGGS)₆] in the TAB2.4 protein. Using primers HR061F and HR061R(HR061F: 5′-ACCGTTAGCAGCGGTGGTGGCGGTTCGGGTGGCGGAGGCAGCGGTGGAGGGGGCTCTGGGG GCGGCGGTTCCGGTGGAGGTGGAAGTGGC-3′ and HR061R: 5′-ACCGCCGCCCCCAGAGCCCCCTCCACCGCTGCCTCCGCCACCCGAACCGCCACCACCGCTGC TAACGGTCACGCTGGTCCCTTGACC-3′) for inserting 15-aa (GGGGS)₃ sequence whose nucleotide sequence is shown in capitals. A two-step regular Quikchange mutagenesis (Stratagene, CA) PCR reaction was performed followed by digestion with DpnI enzyme. Two μL out of 50 μL PCR product was transformed into E. coli TOP10F′ chemically competent cells followed by selection of transformants on LA+Cm10+0.1 CTX plates. Plasmid DNAs from 16 clones were amplified by Templiphi-100 amplification kit (Amersham Biosciences) and sequenced to confirm the insertion of extra sequences. Eleven out of 16 clones were found to have the desired insertion. Complete sequencing of the entire fusion gene of plasmid pSW239.1 revealed no additional mutations elsewhere in the gene. Finally, plasmid pSW239.1 was selected as TAB2.4 molecule, sequence ID NO: (TAB2.4), as shown in FIG. 1A. The amino acid sequence of TAB2.4 is shown in FIG. 1.

Example 3 Combinatorial Consensus Mutagenesis of TAB2.4

To improve the expression of the TAB2.4 protein, a combinatorial consensus mutagenesis approach as described in WO US04/30085, incorporated by reference, herein, including any drawings and was pursued by targeting 12 amino acid residues in the frame work regions of vH and vL domains using plasmid pSW239.4 as a template. These 12 residues (8 positions in vH and 4 positions in vL) were identified as being significantly different (<10% abundance) compared to a typical human antibody sequence. 21 mutations were made among these 12 sites, some having more than one substitution. Using a modified version of Multi-site Quikchange Mutagenesis (Stratagene, CA) protocol as described before in WO US04/30085, incorporated by reference, herein, including any drawings, CCM libraries ME367 and ME368 with combined primer concentrations of 0.4 μM and 2 μM, respectively, were constructed employing 21 phosphorylated primers as shown in Table 1.

TABLE 1 Combinatorial consensus mutagenesis primers Oligo's: Name Sequence (5′ > 3′) Length (bp) vH HD8G [Phos]GTTACAGCAGTCAGGCGCGGAGTTGGTGAAACCGGGC 37 HH32M [Phos]CACCTTTACCGACATGGCCATTCACTGGGTAAAACAG 37 HH32I [Phos]CACCTTTACCGACATTGCCATTCACTGGGTAAAACAG 37 HA33G [Phos]CTTTACCGACCATGGCATTCACTGGGTAAAACAGAAC 37 HA33W [Phos]CTTTACCGACCATTGGATTCACTGGGTAAAACAGAAC 37 HA33Y [Phos]CTTTACCGACCATTATATTCACTGGGTAAAACAGAAC 37 HN40R [Phos]CTGGGTAAAACAGCGCCCGGAACAGGGCCTGGAGTGG 37 HN40A [Phos]CTGGGTAAAACAGGCGCCGGAACAGGGCCTGGAGTGG 37 HN40P [Phos]CTGGGTAAAACAGCCGCCGGAACAGGGCCTGGAGTGG 37 HF51I [Phos]GATTGGGTATATTAGCCCGGGTAATGATGACTTTAAG 37 HF57T [Phos]GTAATGATGACACCAAGTATAACGAACGCTTTAAAG 36 HR62K [Phos]GTATAACGAAAAATTTAAAGGTAAAGCCACCCTGAC 36 HR62S [Phos]GTATAACGAAAGCTTTAAAGGTAAAGCCACCCTGAC 36 HV80L [Phos]GTCCACTGCTTACCTGCAGCTGAACAGTCTCACGTCAG 38 HV80M [Phos]GTCCACTGCTTACATGCAGCTGAACAGTCTCACGTCAG 38 vL LS5T [Phos]GATATTGTCATGACCCAATCTCCGTCATCACTGCCC 36 LA53N [Phos]CTATTGGGCCTCTAACCGTGAATCCGGTGTTCCAGATC 38 LA53T [Phos]CTATTGGGCCTCTACCCGTGAATCCGGTGTTCCAGATC 38 LK79E [Phos]CATTTCGTCTGTGGAAACAGAAGACCTGGCTGTCTAC 37 LK79Q [Phos]CATTTCGTCTGTGCAGACAGAAGACCTGGCTGTCTAC 37 LV105E [Phos]GTACTAAATTAGAACTCAAAACACCGGTGTCAGAAAAAC 39 Sequence of primers used for combinatorial consensus mutagenesis (CCM) of TAB2.4 protein. Primer name corresponds to the amino acid to be changed in the light (L) or heavy (H) chain, its position, and the intended mutation (mutated codon shown in upper case). So, HD8G corresponds to Asp (D) at position 8 of the heavy (H) chain to be changed to Gly (G). The numbering is based on the Kabat system of either light or heavy chains. All primers were designed to the sense strand.

After mutagenesis and DpnI digestion, 1.5 μL out of 25 μL PCR reaction mix was transformed into E. coli TOP10F′ cells followed by selection on LA+Cm20+0.1 CTX plates. 96 clones from each library were initially screened for improved expression in 96-well microtiter plates as described below. Statistical analysis of the sequence to activity data revealed that 5 of the 21 mutations included in the library design were detrimental for binding. Thus, new libraries were designed without the primers coding for those mutations (light chain H32M, H32I, A33G, A33W and A33Y). These new libraries were named ME374, ME375, and ME377. ME374 contained all 16 mutations at 0.4 μM primer concentration, ME375 had all 16 at 0.1 μM primer concentration, and ME377 had mutations D8G, N40A, N40P, V80L in the heavy chain and A53T in the light chain.

Example 4 Screening of CCM Libraries

Libraries pME367 and pME368 were plated onto agar plates containing LB medium and 5 mg/L chloramphenicol (CMP) and 0.1 mg/L cephotaxime (CTX, Sigma). Colonies from each library (96 clones each including parent) were transferred into 96-well plates containing 100 μL LB+5 mg/L CMP. Plates were incubated at 37° C. in a humidified box with shaking for 24 h as a preculture. Plates were replicated into 100 μL of LB+5 mg/L CMP and grown for 48 h at 37° C. On the day of screening, 100 μL of B-Per reagent (PIERCE) was added into each well and shaken at room temperature for 30 min.

Target Bovine Submaxillary Mucin (“BSM”, Sigma) is a mucin containing the TAG-72 epitope shown previously to react with B72.3 and CC49 (O'Boyle, K P. et al. (1996). Hybridoma 15, 401-408). BSM was coated in high binding capacity 96-well polystyrene plate (Costar #9018) by adding 100 μL of 10 μg/mL BSM in PBS and the plate was incubated at 4° C. overnight. The plates were then washed with PBST (PBS+0.1% Tween 20) and blocked with 200 μL/well of PBST for 2 h at room temp. The plates were then washed three times with PBST. 7 μL of B-Per extract library sample was added to 93 μL/well of PBST. The plate was incubated at room temperature with gentle shaking for 2 h. The plates were then washed three times with PBST. 200 μL of BLA substrate nitrocefin in PBSO (PBS+0.125% Octylglucopyranoside) was added into each well, and the bound BLA activity was measured by monitoring hydrolysis of nitrocefin at wavelength 490 nm at room temperature (t=0) (see FIG. 2 and for nitrocefin assay, see, WO 03/105757, incorporated by reference herein, including any drawings). Statistical analysis of the sequence to activity data revealed that 5 of the 21 mutations included in the library design were detrimental for BSM binding (see e.g., FIG. 3). For each mutation in the library, the statistical analysis results in a parameter determined from the experimental data. If a mutation improves either expression or binding or another measurable variable, the parameter will be positive in value or negative in value if the mutation is detrimental. The parameter is based on a logarithmic value such that a parameter of 1 means that the mutation provides a ˜10-fold improvement. The parameter has to be analysed with regards to the number of times that mutation was observed in the library. The more a mutation was observed, the more credible the parameter value becomes. Thus, new libraries were designed without primers coding for those mutations (light chain H32M, H32I, A33G, A33W and A33Y). One plate each of libraries ME374, ME375 and ME377 were screened as previously described except that LB+10 mg/L CMP was used as the growth media. Also, total BLA activity (expression) was measured a 1/10 dilution of the B-per extract in PBSO by adding 20 μL sample dilution to 180 μL PBSO and by monitoring hydrolysis of nitrocefin at wavelength 490 nm at room temperature.

Finally, a comparison of binding was determined as follows. After BSM bound BLA activity was measured at t=0, the plates were incubated 1 h at room temperature with gentle shaking. The plates were then washed three times with PBST. The remaining bound BLA activity (t=1) was measured. The ratio of the bound activity after an hour incubation t=1 over the bound BLA activity at t=0 provides a comparison of off-rates. FIG. 4 shows the screening data for libraries ME374, ME375 and ME377 where many variants show a bound/input ratio higher than the average of TAB2.4 clones.

In FIG. 5, statistical analysis of the sequence to screening data shows that a few mutations seem beneficial for increased expression of TAB2.4.

From the screen, 22 clones were picked for further analysis. Glycerol stocks of the clones, plus parent TAB2.4 and a control CAB 1.2, which binds carcinoembryoinc antigen (“CEA”), but does not bind TAG-72, were streaked out on LA+5 mg/L CMP agar plate. Four colonies from each variant were inoculated in 100 μL of LB+10 mg/L CMP in a 96-well plate and grown overnight at 37° C. The plate was replicated into three 96-well plates containing 100 μL of LB+10 mg/L CMP and grown 48 h at 37° C. B-per extracts of the three plates (triplicate) were prepared as previously described. BLA activity, binding to BSM and off-rate were also measured as previously described. Samples were diluted 10-fold in PBS for the measurement of BSM binding.

Data in FIG. 6 show that a few clones have better expression and binding to BSM. However, careful analysis of the sequences revealed that some clones had mutations in the linker region between the vL and the vH which could affect the amount of dimer and multimer present in the B-per extract and thus affect the binding data. The clones having linker mutations were not further analyzed.

The seven best expressing/binding clones from the data and sequence analysis, and a TAB2.4 control, were grown in a tube containing 2 mL LB+10 mg/L CMP overnight at 37° C. Then, 200 μL of the culture was transferred to 25 mL TB media+10 mg/L CMP in triplicate and grown 48 h at 37° C. One mL of the culture was pelleted and one mL of B-per reagent was added and incubated 60 min with shaking. The B-per extract was spun and the supernatant was transferred to a new tube. Each sample was tested for BLA activity, BSM binding (serial dilution) and off-rate as described previously. The samples were compared in an anti-BLA western blot for intactness of the fusion protein. For the western blot, each of the samples were prediluted so that only 50 ng fusion protein in each well was loaded. The 50 ng was diluted 2/3 into reducing agent by mixing 60 μL of each sample with 30 μL 4X LDS Sample Buffer and Sample Reducing Agent (Invitrogen). The gel loading samples were heated for 5 min at 85° C. 15 μL of each sample was loaded for the gel that was to be stained into separate wells of NuPAGE 4-12% Bis-Tris gels.

Protein was then transferred from the SDS-PAGE gel onto a PVDF membrane using transfer buffer (Invitrogen) and run at 25V constant voltage for 60 min Membrane was blocked by immersing it in a 2.5% BSA solution (Blocker BSA in Tris Buffered Saline with 0.1% tween-20 (TBST) and shaking for 60 min Membrane was immersed into the primary antibody solution and shaken for 60 min (Abgent mouse anti-BLA mAb was diluted 1:10,000 in TBST). Membrane was rinsed 3×5 min in TBST. Membrane was immersed into the secondary antibody solution (goat anti-mouse IgG:HRP (Pierce) diluted 1:20,000 in TBST) and shaken for 60 min Membrane was rinsed 3×10 min in TBS-T.

2 mL ECL Plus (Amersham Biosciences) detection solution was made by adding 50 μL of solution B to 2 mL of solution A. The detection solution was pippetted over the membrane surface. After 5 min incubation with the detection solution, excess reagent was drained off and the membrane was placed protein-side down on Storm Imager scanning bed. A scan was done using the blue fluorescence/chemifluorescence mode. Densitometry was used to determine the percentage of intact protein. The western membrane was scanned using Storm Imager using the Image Quant program to do desitometry on the bands for both intact and degraded material. Cross-section lines were used to report band intensity as area under the curve (AUC) and values were calculated in terms of percent intact, percent degraded as BLA and total magnitude of band intensity (AUC).

Clone pME374.4 showed better expression (3.5-4-fold better, see FIG. 7) and intactness (˜90% vs ˜50%, see FIG. 8) than the parent TAB2.4 and equivalent binding and off-rate to coated BSM and was picked as the next generation and named TAB2.5. TAB2.5 contains mutations V80L in the vH region of the scFv fragment, and S5T, A53T and K79E in the vL region compared to TAB2.4. A binding curve to coated BSM showed that the clones tested had higher apparent affinities than TAB2.4 (see FIG. 9).

Example 5 Expression and Purification of TAB2.4 and TAB2.5

The cell was disrupted with B-PER as follows. 2.5 mL B-PER Reagent (in Phosphate Buffer, Pierce Biotechnology Inc., product #78266) per gram of frozen E. coli cell paste was added. Benzonase Nuclease (Novagen, product #70664-3) was also added at a dilution of 1:1000 to hydrolyze DNA. Mixture was stirred vigorously for 60 min at room temperature. Cell debris was removed by centrifugation at 4° C. for 20 min and 12,000 rpm. Pellet was discarded.

Fusion protein was captured via PBA affinity chromatography. A 5 mL PBA column (m-Aminophenylboronic acid immobilized onto agarose beads from Sigma, product #A-8312) was equilibrated with 25 mL TEA buffer (20 mM triethanolamine, pH 7) prior to loading crude protein. After sample loading, the column was washed first with 25 mL TEA buffer, and a second time with 25 mL TEA/NaCl buffer (20 mM triethanolamine, 0.5 M NaCl, pH 7). β-lactamase fusion protein was eluted with 25 mL borate/NaCl buffer (0.5 M borate/0.5 M NaCl, pH 7) and collected in 5 mL fractions. Eluted fractions were assayed for β-lactamase activity using the nitrocefin plate assay, as described above.

Size exclusion chromatography was used to obtain pure monomer. 5 mL of concentrated TAB protein was loaded onto a Superdex 75 preparative grade column (Amersham Biosciences, product #17-1070-01) equilibrated with PBS. Proteins were separated with a flow rate of 2 mL/min of PBS and collected in 5 mL fractions.

Endotoxin was removed via Detoxi-Gel™. 1-4 mL of concentrated β-lactamase fusion protein was loaded onto a 10 mL Detoxi-Gel™ (immobilized polymixin-B, Pierce, product #20339) column equilibrated with PBS. The sample was left bound to the resin for 2.5 h before eluting with PBS. 15.1 mL fractions were collected. A typical SDS-PAGE gel of the fractions eluted is shown in FIG. 10. Individual fractions were assayed for β-lactamase activity using the nitrocefin plate assay and for endotoxin using the BioWhittaker QCL-1000 Chromogenic Endpoint LAL assay. Endotoxin units per mg of TAB protein were calculated. The maximum limit for in vivo murine studies was 5 U/mg.

Example 6 Binding of TAB2.4 and TAB2.5 to TAG-72 Preparations

Antigens for binding were coated as follows. All assays were performed using high binding capacity 96-well plates (Costar 9018). BSM (Sigma) was coated at 10 μg/mL in 100 μL PBS for either 2 h at room temperature or >16 h at 4° C. Tumor extract was coated at 1 μg/well in PBS and the plate was air dried at 25° C., O/N in an incubator. Tumor extract was generated from a pool of several LS174T xenografts from mice. Tumor pool was treated with T-per (Pierce #78510) (1 mL per 100 mg of tumor) and Halt protease inhibitor (PIERCE, #78410, 100×) was added 1× concentration and the tumor was homogenized. The T-per suspension was shaken at RT for 20 min to resuspend cells and then spun at 10,000 rpm for 15 min. The supernatant was collected as tumor extract (TE) and was aliquoted and frozen at −80° C. BCA (Biorad) assay was performed on the cell lysate to determine protein concentration. For antigen CA72-4 which is a purified form of TAG-72 purified from human fluids available commercially (Bioprocessing Inc., stock at 43,504 U/mL), 100 μL of a 1/1000 dilution was coated in PBS for 16 h at 4° C. After coating, wells were washed three times with PBST and blocked for 2 h with 200 μL PBST. Various concentrations of TAB molecules were added in a final volume of 100 μL in PBST and incubated for 2 h at room temperature with shaking. Unbound material was washed three times with PBST and bound TAB was detected by adding 200 μL nitrocefin solution followed by OD at 490 nm for 15 min.

TAB2.5 bound to all tested TAG-72 antigens. Binding signal varied depending on the antigen and CA 72-4 antigen gave low binding signal compared to BSM and tumor extract (see FIG. 11). TAB2.4 and TAB2.5 bound to coated BSM with similar affinity (see FIG. 12) and had similar off-rates (see FIG. 13, as measured above). In all cases, saturation of the binding signal was not obtained at the highest concentration of TAB tested.

Competition assays were also performed. BSM or tumor extract were coated in a 96-well plate as described previously. After washing and blocking the wells, 5 000 U of TAB2.5 was added with various concentrations of competitors in a final volume of 100 μL in PBST. The competitors used were BSM (Sigma, assuming a molecular weight of 150 kDa), STn biotinylated multimer (TAG-72, Glycotech #01-059), tumor extract (TE) from LS174T cells and CA 72-4 (BioProcessing). Biotinylated STn multimer is a purified synthetic form of TAG-72 that may also be recognized by TAB conjugate. TAB2.5 in the presence of competitor was incubated for 2 h at room temperature with agitation and unbound material was washed three times with PBST and bound TAB2.5 was measured by adding 200 μL nitrocefin solution and reading kinetic OD at 490 nm for 15 min FIGS. 14 and 15 show that BSM inhibits binding of TAB2.5 to tumor extract and BSM with IC₅₀'s of ˜300 nM and ˜200 nM, respectively. TAB2.5 binding to either BSM or tumor extract was not inhibited by tumor extract, CA72-4 or STn in the conditions tested (up to 150 μg/mL for tumor extract, up to ˜2200 U/mL for CA72-4 and up to 850 nM for STn).

Example 7 Construction of Charge Variant Libraries

To study the impact of protein net charge on pharmacokinetic parameters of the TAB2.5 protein, we constructed 4 libraries to either increase or decrease net charge based on the scFv, or on the beta-lactamase portion of the molecule. Using a modified version of Multi-site Quikchange Mutagenesis (Stratagene, CA) protocol as described before (see, for example, WO US 04/30085, which is incorporated by reference, herein, including any drawings), 4 libraries were made to either increase or decrease the net charge of TAB2.5 with libraries based in the scFv, and two based in beta-lactamase. Library ME384 was created in beta-lactamase to increase the charge by replacing certain non-conserved positively charged residues with arginine or lysine, and ME385 was created to decrease the net charge by substituting aspartic acid or glutamic acid. Libraries ME386 and ME387 were created in the same manner in the scFv, to increase or decrease the net charge respectively. Libraries ME384 and ME385 were created using 17 and 20 phosphorylated primers respectively, as shown in Table 2. Libraries ME386 and ME387 were created using 14 and 15 phosphorylated primers respectively, as shown in Table 3. All primers were HPLC purified. The 4 individual reactions were set up with combined primer concentrations of 0.4 μM, using pME374.4 as template. After mutagenesis and DpnI digestion, 1.5 μL out of 25 μL PCR reaction mix was transformed into E. coli TOP10F′ cells followed by selection on LA+20 mg/L CMP+0.1 mg/L CTX plates. 96 clones from each library were screened for improved expression in 96-well microtiter plates as described below.

TABLE 2 Primers for TAB2.5 charge mutagenesis Name Sequence (5′-3′) Length ME384 beta-lactamase charge increase BE5R [Phos]AACACCGGTGTCACGCAAACAGCTGGCGGAGGTGGTCG 38 BE10K [Phos]AAACAGCTGGCGAAAGTGGTCGCGAATACGATTACC 36 BD76R [Phos]TTTTAGGTGGGCGCGCCATTGCTCGCGGTGAAATTTC 37 BD86R [Phos]GAAATTTCGCTGCGCGATGCGGTGACCAGATACTGG 36 BE124R [Phos]ACAGGTACCGGATCGCGTCACGGATAACGCCTCCCTG 37 BD127R [Phos]GATGAGGTCACGCGCAACGCCTCCCTGCTGCGC 33 BE171R [Phos]TGGCATGCCCTATCGCCAGGCCATGACGACGCGGGTC 37 BD185K [Phos]CCGCTCAAGCTGAAACATACCTGGATTAACGTGCCG 36 BE196R [Phos]CCGAAAGCGGAACGCGCGCATTACGCCTGGGGCTATC 37 BD217R [Phos]CCGGGTATGCTGCGCGCACAAGCCTATGGCGTGAAAAC 38 BE241R [Phos]AAACATGGCGCCGCGCAACGTTGCTGATGCCTCAC 35 BD245R [Phos]GGAGAACGTTGCTCGCGCCTCACTTAAGCAGGGCATC 37 BE279K [Phos]CAACTGGCCCGTGAAAGCCAACACGGTGGTCGAGAC 36 BE285R [Phos]CAACACGGTGGTCCGCACGAGTTTTGGTAATGTAGC 36 BE331R [Phos]GGCCTTTATTCCTCGCAAGCAGATCGGTATTGTGATG 37 BE351K [Phos]CCGGCACGCGTTAAAGCGGCATACCATATCCTCGAG 36 BE358K [Phos]ATACCATATCCTCAAAGCGCTACAGTAGGAATTCGAG 37 ME385 beta-lactamase charge decrease BK6E [Phos]ACCGGTGTCAGAAGAACAGCTGGCGGAGGTGGTCGCG 37 BK21E [Phos]TACCCCGCTGATGGAAGCCCAGTCTGTTCCAGGCATG 37 BK37E [Phos]TATTTATCAGGGAGAACCGCACTATTACACATTTGG 36 BK45E [Phos]TACACATTTGGCGAAGCCGATATCGCGGCGAATAAAC 37 BK52E [Phos]ATCGCGGCGAATGAACCCGTTACGCCTCAGACCCTG 36 BR80E [Phos]GATGCCATTGCTGAAGGTGAAATTTCGCTGGACGATG 37 BR91E [Phos]GATGCGGTGACCGAATACTGGCCACAGCTGACGGG 35 BK99E [Phos]AGCTGACGGGCGAACAGTGGCAGGGTATTCGTATG 35 BR105D [Phos]TGGCAGGGTATTGATATGCTGGATCTCGCCACCTAC 36 BR133D [Phos]ACGCCTCCCTGCTGGATTTTTATCAAAACTGGCAGCC 37 ME384 beta-lactamase charge increase BK143D [Phos]CAGCCGCAGTGGGATCCTGGCACAACGCGTCTTTAC 36 BK164D [Phos]GCGCTGGCGGTCGATCCTTCTGGCATGCCCTATGAG 36 BK180D [Phos]GACGCGGGTCCTTGATCCGCTCAAGCTGGACCATAC 36 BK183D [Phos]CTTAAGCCGCTCGATCTGGACCATACCTGGATTAAC 36 BK193E [Phos]GATTAACGTGCCGGAAGCGGAAGAGGCGCATTACGC 36 BK249E [Phos]TGATGCCTCACTTGAACAGGGCATCGCGCTGGCGCAG 37 BR261E  [Phos]AGTCGCGCTACTGGGAAATCGGGTCAATGTATCAGGG 37 BK309E [Phos]GGCTCCCCCGGTCGAAGCGTCCTGGGTCCATAAAAC 36 BK332E [Phos]TTTATTCCTGAAGAACAGATCGGTATTGTGATGCTC 36 BR349E  [Phos]TCCGAACCCGGCAGAAGTTGAGGCGGCATACCATATC 37 Sequence of primers used for beta-lactamase mutagenesis of TAB2.5 protein. Primer name corresponds to the amino acid to be changed, its position, and the intended mutation (mutated codon shown in upper case). All primers used in beta-lactamase mutagenesis are named starting with B. So, BE5R corresponds to Glu (E) at position 5 of beta-lactamase to be changed to Arg (R). The numbering is based on the first residue of beta-lactamase. All primers were designed to the sense strand.

TABLE 3 Primers for TAB2.5 charge mutagenesis Name Sequence (5′-3′) Length ME386 scFv charge increase HD8R [Phos]GTTACAGCAGTCACGCGCGGAGTTGGTGAAACCGGG 36 HE10R [Phos]CAGTCAGATGCGCGCTTGGTGAAACCGGGCGCGAG 35 HE42R [Phos]TAAAACAGAACCCGCGCCAGGGCCTGGAGTGGATTGG 37 HE46K [Phos]GGAACAGGGCCTGAAATGGATTGGGTATTTCAGCCC 36 HE61R [Phos]CTTTAAGTATAACCGCCGCTTTAAAGGTAAAGCCAC 36 HD72K [Phos]ACCCTGACGGCGAAAAAATCGTCGTCCACTGCTTAC 36 HE85R [Phos]CAGTCTCACGTCACGCGATAGCGCGGTGTATTTCTG 36 LD1R [Phos]GGCGGTGGATCTCGCATTGTCATGACCCAATCTCC 35 LE17K [Phos]GTGAGTGTTGGAAAAAAGGTGACGCTGAGTTGCAAAAG 38 LE55K [Phos]GCCTCTACCCGTAAATCCGGTGTTCCAGATCGTTTC 36 LD60K [Phos]TCCGGTGTTCCAAAACGTTTCACCGGCAGTGGTTC 35 LD70K [Phos]GGTTCGGGCACTAAATTTACACTGTCCATTTCGTC 35 LE79K [Phos]ATTTCGTCTGTGAAAACAGAAGACCTGGCTGTCTAC 36 LE81K [Phos]GTCTGTGGAAACAAAAGACCTGGCTGTCTACTATTG 36 ME387scFv charge decrease HK13E [Phos]TGCGGAGTTGGTGGAACCGGGCGCGAGCGTAAAGATTTC 39 HK19E [Phos]GGCGCGAGCGTAGAAATTTCTTGTAAAGCATCCGG 35 HK23E [Phos]AAAGATTTCTTGTGAAGCATCCGGCTACACCTTTAC 36 HK38E [Phos]CATTCACTGGGTAGAACAGAACCCGGAACAGGGCCTG 37 HK58E [Phos]TAATGATGACTTTGAATATAACGAACGCTTTAAAGG 36 HR62D [Phos]TAAGTATAACGAAGATTTTAAAGGTAAAGCCACCCTG 37 HK64E [Phos]ATAACGAACGCTTTGAAGGTAAAGCCACCCTGACGGC 37 HK73D [Phos]CTGACGGCGGACGATTCGTCGTCCACTGCTTACCTG 36 LK18D [Phos]GAGTGTTGGAGAAGATGTGACGCTGAGTTGCAAAAG 36 LK24E [Phos]GACGCTGAGTTGCGAAAGCTCCCAAAGCCTGCTATAC 37 LK39E [Phos]TGGTATCAGCAGGAACCAGGCCAGTCTCCTAAATTG 36 LK45E [Phos]AGGCCAGTCTCCTGAATTGCTGATCTATTGGGCCTC 36 LR54E [Phos]TTGGGCCTCTACCGAAGAATCCGGTGTTCCAGATCG 36 LK103E [Phos]GGGCGGGTACTGAATTAGTTCTCAAAACACCGGTG 35 LK107E [Phos]TAAATTAGTTCTCGAAACACCGGTGTCAGAAAAACAG 37 Sequence of primers used for scFv mutagenesis of TAB2.5 protein. Primer name corresponds to the amino acid to be changed in the light (L) or heavy (H) chain, its position, and the intended mutation (mutated codon shown in upper case). So, HD8R corresponds to Asp (D) at position 8 of the heavy chain to be changed to Arg (R). The numbering is based on the Kabat system for both the light and heavy chains. All primers were designed to the sense strand.

Example 8 Screening of Charge Variant Libraries

One plate each of libraries ME384, ME385, ME386, ME387 were screened as previously described except that LB+10 mg/L CMP was used as the growth media and the cultures were grown at 30° C. for 48 h. Expression, measured as total BLA activity, BSM binding and off-rate were measured for all the clones and parent TAB2.5.

Many variants containing up to 3 charge reversal mutations in the BLA portion of the fusion were identified that expressed and bound in a similar fashion to TAB2.5. Also, many variants were identified that contained up to 7 charge reversal mutations in the scFv portion of the fusion protein and showed good expression and binding to BSM, similar to TAB2.5 parent (see FIG. 16). For further analysis, clones that had similar BSM binding and expressed well and that contained a range of net charges were picked. The B-per extracts for these clones were tested in quadruplicates (for expression and BSM binding) after being grown in 96-well format at 30° C. for 48 h. Furthermore, the choice of clones was narrowed down to 11 clones plus template TAB2.5. The mutations, net charge and theoretical pI of the clones is shown in Table 4. Clones that had similar binding to BSM and good enough expression were chosen. These were grown in 25 mL shake flasks containing TB medium with 10 μg/mL CMP for 48 h at 30° C. Expression (BLA activity), BSM and tumor extract (TE) binding and off-rates, intactness using western blot were measured and compared with wt template TAB2.5. A summary of the results is shown in Table 5 where many clones have characteristics similar to TAB2.5.

TABLE 4 List of clones selected for further analysis and their characteristics. Clone name # of mutation Mutations Net charge pI pME384.36 3 E10K, D86R, E196R 7.4 8.9 pME385.95 4 K21E, K37E, K99E, R261E −6.6 5.7 pME386.10 7 lD1R, lE17K, lE55K, lD60K, lD70K, lE79K, 15.3 9.3 lE81K pME386.19 4 lE17K, lD60K, lD70K, lE79K 9.4 9.0 pME386.36 6 hE46K, lD1R, lE55K, lD70K, lE79K, lE81K 13.3 9.2 pME386.41 3 lE55K, lD70K, lE79K 7.4 8.9 pME386.74 5 hE42R, lD1R, lE17K, lD70K, lE81K 11.4 9.1 pME387.28 4 hK13E, hK23E, lK24E, lK103E −6.6 5.7 pME387.64 6 hK13E, hK19E, hK64E, lK24E, lK45E, lK103E −10.6 5.3 pME387.75 5 hK13E, hK23E, lK24E, lK45E, lK103E −8.6 5.5 pME387.91 7 hK13E, hK23E, lK18D, lK24E, lK45E, lR54E, −12.6 5.2 lK103E TAB2.5 0 1.4 7.7 h or l indicate mutations in the heavy or light chain, respectively.

TABLE 5 Summary of the biochemical data generated for selected charge variant clones. BSM TE Clone BSM off- TE off- name Expression binding rate binding rate Western pME384.36 = − = − = = pME385.95 − − =+ − = − pME386.10 −− = −−− = = − pME386.19 = = = = = = pME386.36 − − −−− = = −−− pME386.41 = = + = = − pME386.74 − = =− = = −− pME387.28 =+ = + − = = pME387.64 − − −− − = − pME387.75 = = = − = − pME387.91 − − − − = = TAB2.5 = = = = = =

Example 9 Construction and Testing of TAB2.6

AmpC or TAB2.5 was replaced with TEM-4 β-lactamase, which is approximately 100 amino acids smaller and may affect plasma clearance. Plasmid pME381.10 contains TAB2.5 and suitable restriction sites to swap β-lactamase. TEM-4 was amplified from a mutant of pLITMUS39 (New England Biolabs, Beverly, Mass.), a plasmid having increased activity on cephalosporins [Long-McGie, J., A. D. Liu and V. Schellenberger (2000) Biotechnol. Bioeng. 68, 121-125, Rapid in vivo evolution of a β-lactamase using phagemids] using primers ME363F (5′-ACTAAATTAGTTCTCAAAACACCGGTGCACCCAGAAACGCTGGTGAAAG-3′) and ME363R (5′-CGTTTGATCTCGAGTGCGGCCGCAAGCTTGTCGACGGAGCTCGTTACCAATGCTTAATCAGT GAGG-3′) containing restriction sites PinAI and NotI. The PCR product was purified using a Qiaquick PCR purification kit (Qiagen), and both pME381.10 and PCR product were digested with PinAI and NotI. The approx. 850 bp insert fragment and 4.1 kb vector fragment were gel purified. Fragments were ligated together overnight, followed by purification and transformation into E. coli TOP10F′ (Invitrogen, Carlsbad, Calif.) competent cells and selection on LA+20 mg/L CMP+0.1 mg/L CTX plates. Two colonies were selected and sequenced, and plasmid pME382.1 was chosen as TAB2.6. TAB2.6 was expressed and a B-per extract was prepared as described previously. BLA activity and binding to BSM was measured. TAB2.6 expressed, but the amount of BLA activity observed is low compared to TAB2.5 (10-fold less), data not shown.

Example 10 Construction and Testing of TAB2.7

Another version of β-lactamase replacing ampC with a stabilized version of ampC created in previous experiments (see, Amin, N., Liu, A. D., Ramer, S., Aehle, W., Meijer, D., Metin, M., Wong, S., Gualfetti, P., Schellenberger, V. (2004) Protein Engineering, Design, and Selection, 17, 787-793). Plasmid pME381.10 contains TAB2.5 and suitable restriction sites to swap β-lactamase. Our stabilized β-lactamase was PCR amplified from plasmid pNA04.17 using primers ME365F (5′-ACTAAATTAGTTCTCAAACACCGGTGTCAGAAAAACAGCTG-3′) and ME365R (5′-CGTTTGATCTCGAGTGCGGCCGCAAGCTTGTCGACGGAGCTCGTTACTGTAGCGCCTCTAGG ATATGG-3′) containing restriction sites PinAI and NotI. The PCR product was purified using a Qiaquick PCR purification kit (Qiagen), and both pME381.10 and PCR product were digested with PinAI and NotI. The approximately 1.1 kb insert fragment and 4.1 kb vector fragment were gel purified. Fragments were ligated together overnight, followed by transformation into E. coli TOP10F′ (Invitrogen, Carlsbad, Calif.) competent cells and selection on LA+20 mg/L CMP+0.1 mg/L CTX plates. One colony was selected and sequenced, and plasmid pME388.1 was chosen as TAB2.7.

TAB2.5 and TAB2.7 were grown in 25 mL shake flask cultures and B-per extracts were prepared as described previously. Expression of TAB2.7 was 5-fold higher than TAB2.5.

Both molecules were tested for protease stability. Thermolysin protease was prepared at a stock concentration of 2.5 mg/mL in imidazol/HC1 buffer. The stock solution was then diluted 5-fold in series to give thermolysin concentrations 500 μg/mL, 100 μg/mL, 20 μg/mL, and 4 μg/mL and one without protease. 87 μL of each extract was added to 800 μL buffer containing the various concentration of thermolysin and incubated 1 h at 37° C. in a water bath.

The protease was then inactivated by adding 200 μL of 10 mM EDTA. All samples were tested for remaining BLA activity by adding 20 μL of the sample to 180 μL of nitrocephin substrate. These plates were read at 490 nm in 5 min at room temperature in a kinetic assay. The samples were also compared for remaining BSM binding activity as previously described. BSM binding was not measured for protease-treated TAB2.5 because the BLA portion of the molecule was too unstable to have a read out for the assay.

To test the effect of protease on the TAB scFv, TAB2.7 was tested, which has the exact same scFv as does TAB2.5, but with a much more stable BLA. As can be seen from FIG. 17, the stabilized version of BLA in TAB2.7 is more protease stable than the one in TAB2.5 as expected. TAB2.7's binding to BSM was not affected until the highest concentration of thermolysin used of 2.5 mg/mL (see FIG. 18). The data indicate that the scFv portion of TAB2.5, as well as TAB2.7, is more stable to thermolysin treatment than the BLA portion of the fusion protein.

Example 11 Cysteine Bond Between Light and Heavy Chain of svFv

In an effort to stabilize TAB2.7, we placed a disulfide bond between the heavy and light chains of the scFv by substituting a cysteine in each chain. The position of the disulfide bond was determined by modeling the protein (see, for example, V. S. Dani, C. Ramakrishnan and R. Varadarajan (2003) Protein Engineering 16, 187-193). Plasmid pME388.1 (TAB2.7) was modified using a modified version of Multi-site Quikchange Mutagenesis (Stratagene, CA) protocol as described before (see, for example, WO US 04/30085, which is incorporated by reference, herein, including any drawings). Using template pME388.1, the reaction was set up with 100 ng each of 2 phosphorylated primers. TABLL46C; 5′-[Phos]CAGTCTCCTAAATGCCTGATCTATTGGGCCTCTAC-3′ for replacement of light chain Leu46 with Cys and TABHA101C; 5′-[Phos]AGCCTTAACATGTGCTATTGGGGTCAAGGGACCAGC-3′ for replacement of heavy chain Ala101 with Cys. After mutagenesis and DpnI digestion, 1.5 μL out of 25 μL PCR reaction mix was transformed into E. coli TOP10F′ cells followed by selection on LA+20 mg/L+0.1 mg/L CTX plates. 30 colonies resulted, and 12 were picked for sequencing. Sequencing of these clones revealed that 4 contained mutations (3 1L46C, 1 hA101C), but none of them had both together. Clone pME395.1 (hA101C) was chosen for a new round of mutagenesis with 100 ng of the TABLL46C primer alone. This reaction was performed as above, and 12 colonies resulted. All 12 were picked for sequencing, and pME403.3 had the additional cysteine. This construct was chosen for further stability and expression studies.

The variant was expressed and a B-per extract was prepared as described previously. BLA activity and binding to BSM were measured. pME403.3 expressed well, but ˜35% less than TAB2.7 and the B-per extract contained only 35% intact protein compared to 85% for TAB2.7 (data not shown). The binding affinity to coated BSM was reduced by ˜40-fold (see, FIG. 19). The data thus suggest that mutations of residues 1L46 and hA101 to cysteines affected stability and binding affinity of the protein. More variants could be designed and tested, according to this protocol.

Example 12 Thermal Stability of TAB2 Variants

DSC thermograms were collected on a VP DSC from Micorocal. Buffer conditions were phosphate buffered saline at pH 7.4 and protein concentration was ˜0.7 mg/mL based on BLA activity. Data was collected from 25 to 90° C. with a scan rate of 90° C./hour. TAB2.5 is more stable (˜2° C.) than TAB2.4 and may be less prone to aggregation (see, FIG. 20). The transition is broader and less cooperative.

Example 13 Immunohistochemistry of TAB2.5

Immunohistochemistry of TAB2.5 was performed on an Accumax A301 various cancer array and A203 Colon Cancer array (Petagen) using the following method:

-   Deparaffinize with Histo-Clear, 2× for 5 min (National Diagonistics,     catalog #HS-200)     -   Rehydrate in graded ethanol series (2 min each of 100%, 95%,         75%, 50% ethanol, DI water)     -   Heat-Based Antigen Retrieval (30 min, 1 mM EDTA, pH 8.0 at 90°         C.)     -   Incubate sections in PBS containing 1% normal goat serum for 20         min     -   Block endogenous peroxidase activity with DAKO Peroxidase         Blocking Solution for 10 min     -   Wash slides for 1 min in TBS     -   Incubate sections with TAB2.5 for 30 min (10 μg/mL, diluted in         PBS containing 1% normal goat serum)     -   Wash slides for 5 min in TBS     -   Incubate sections with ROPO2 (see, for example, U.S. Ser. No.         60/636,002, which is incorporated by reference, herein,         including any drawings) for 30 min (0.15 μg/mL, anti-BLA rabbit         polyclonal, diluted in PBS containing 1% normal goat serum)     -   Wash slides for 5 min in TBS     -   Incubate sections with DAKO anti-rabbit antibody for 30 min         (DakoCytomation Rabbit Envision+System-HRP, DAB, catalog #K4010)     -   Wash slides for 5 min in IBS     -   Incubate sections in DAKO Peroxidase substrate solution for 3-5         min until desired staining intensity develops     -   Rinse slides in DI water     -   Counterstain with Haemotoxylin, clear and mount

In this initial assessment of TAB2.5 tissue binding by IHC using a various cancer array, a strong signal was observed for one colon cancer and weaker signals for uterus and stomach cancer sections, while no binding was observed for any of the normal tissues (see FIG. 21). In a colon cancer tissue array, positive TAB 2.5 staining of several human colon tumors ranging from mild to very strong was observed (see FIG. 22). A magnification of one of the colon tumor samples is shown (see FIG. 23).

Example 14 Pharmacokinetics and Tissue Distribution of TAB3.4 in a Xenograft Mouse Model of Human Colorectal Cancer

Female Ncr athymic nude mice, 18-22 g, approximately 6-10 weeks of age, were implanted subcutaneously with approximately 2 million tumor-derived LS174T human colorectal cancer cells. LS174T cells were obtained from the ATCC, passaged through mice and re-isolated to generate TLS174T. When tumors reached approximately 200-300 mm³, 30 animals were administered a single IV bolus injection of TAB2.4 (1 mg/kg) via the tail vein. Three animals were anaesthetized and sacrificed at pre-dosing, 2, 15, 30 min, 1, 2, 4, 8, 24, 48, and 72 h, respectively. Tumors were harvested from each animal at 8, 24, 48, and 72 h, snap frozen in liquid nitrogen, and stored at approximately −70° C. until analysis. Blood was collected via cardiac puncture onto EDTA containing tubers. Blood samples were centrifuged to separate plasma, which was then stored at −70° C. until analysis.

The tissue samples were homogenized on ice in PBS with 15 μg/mL aprotinin (2 mL buffer:gram tissue). The homogenate was mixed with T-per (1:1) (from Pierce) and centrifuged. TAB2.4 concentrations in the tissue supernatant and plasma samples were determined by measuring β-lactamase (BLA) activity using a capture BLA nitrocefin assay, according to the following.

-   -   1. Coat high binding capacity (HBC) plates (Costar #9018) with 5         μg/mL of either chicken polyclonal anti-BLA antibody (PAS         3313/3314), 100 μL/well, 0/N at 4° C.;     -   2. Wash the plate 3× with 1×PBS/0.05% Tween-20 (PBST);     -   3. Block the plate with 250 μL/well of Blocker Casein in PBS         (Pierce #37528) for 2 h at room temperature with gentle shaking;     -   4. Wash the plate 3× with PBST;     -   5. Add 20 μL plasma samples or tissue supernatant to each well,         then diluted it with 80 μL/well of Blocker Casein buffer,         incubate for 2 h at room temperature with gentle shaking;     -   6. Wash 6× with PBST;     -   7. Add 200 μL/well of nitrocefin substrate solution;     -   8. Read kinetics at 490 nm for 15 min.

The results of this experiment demonstrate that TAB2.4 was rapidly eliminated from plasma and localized to the TLS174T tumor (see FIG. 24). High tumor to blood ratio of TAB2.4 concentrations were achieved and sustained.

Example 15 Pharmacokinetics of TAB2.5 in Non-Tumor Bearing Male Sprague Dawley Rats

Three male Sprague Dawley rats, 300-350 g, approximately 6-8 weeks of age, were administered a single IV bolus injection of TAB 2.5 (1 mg/kg) via the femoral vein catheter. Blood samples were drawn via jugular vain catheter at pre-dosing, 2, 5, 15, 30 min 1, 2, 4, 8, 12, 24, and 48 h onto EDTA containing tubes, and were centrifuged to separate plasma, which was then stored at −70° C. until analysis.

Plasma TAB2.5 concentrations were determined by a capture BLA nitrocefin assay described above. The results of this experiment indicated that following an intravenous injection, plasma TAB2.5 disposition was biphasic with a rapid distribution t_(1/2α) of 0.63 h followed by a slow terminal t_(1/2β) of 6 h (see, FIG. 25). More than 50% of drug exposure occurred within 1 h. The drug clearance was 0.27 mL/min and the volume of distribution (16 mL) was similar to the plasma volume.

Example 16 Efficacy of TAB2.5 in a Xenograft Mouse Model of Human Colorectal Cancer

Ncr athymic nude mice, 18-22 g, approximately 6-8 weeks of age, were implanted subcutaneously with 5 million tumor-derived LS174T human colorectal cancer cells. LS174T cells were obtained from ATCC, passaged through mice and re-isolated to generate TLS174T. When the tumors reached the size range of 50-150 mm³, the animals were randomized for tumor volume into two groups with ten animals per group so that there was no significant difference between the groups. The animals were administered vehicle (group 1) or TAB2.5 (1 mg/kg, group 2). Following 24 h, the animals that received TAB2.5 were administered GC-MeI at a dose of 150 mg/kg. All drugs were administered by IV bolus injections via the tail vein. Tumors were measured twice weekly. The average tumor volumes for each group are plotted versus (Study) Days in FIG. 26. This demonstrated that TAB2.5 at 1 m/kg in combination with the prodrug GC-Mel at 150 mg/kg are active in inhibiting the growth of TLS174T tumor cells a mouse model of human colorectal cancer.

Example 17 Construction of TAB2.8

TAB2.8 consists of an scFv fused to ampC (Enterobacter cloacae) β-lactamase. The scFv was based on TAB2.5 scFv (vH-linker-vL), but the heavy and light chains are reversed (vL-linker-vH). The scFv containing the reversed chains was synthesized by DNA2.0 (Menlo Park), also containing restriction sites NcoI and PinAI flanking 5′ and 3′ of the gene respectively. Both pME381.10 (TAB2.5 cloning vector) and the synthesized gene (pG00931) were cut with NcoI and PinAI. The approx. 784 bp insert fragment and 4.4 kb vector fragment were gel purified. Fragments were ligated together overnight, followed by transformation into E. coli TOP10F′ (Invitrogen, Carlsbad, Calif.) competent cells and selection on LA+Cm20+0.1 CTX plates. Two colonies were selected and sequenced, and plasmid pME411.1 was chosen as TAB2.8.

TAB2.8 and TAB2.5 in TOP10F′ were grown in 600 ml of TB-10 μg/ml cmp for 48 h at 30° C. The culture was spun 15 min at 10 000 rpm and the cell lysate was recovered by treating with 50 ml B-PER at room temperature for 60 min and then spinning 15 min at 10 000 rpm. The TAB proteins were purified as described earlier using a 5 ml PBA column. 20 μL of ˜5 mg/ml PBA purified material was loaded onto an analytical size exclusion column (SEC, Phenomenex Biosep-SEC-S 3000; 600×7.8 mm) and the monomer was purified by running the column at 1 mL/min in PBS. The monomer peak was manually collected between 16.5 and 17.5 min of elution. The monomers of TAB2.5 and TAB2.8 were compared in a binding assay against coated BSM and tumor extract (TE) as described previously.

Example 18 TAB2.8 Binding

Bound BLA activity was plotted against the concentration of free TAB to determine K_(D)'s as shown in FIG. 27. The software Graphit ver. 3.01 curve fitting tool for binding to one site was used to calculate the K_(D)'s. TAB2.5 and TAB2.8 have K_(D)'s of 45 and 9.9 nM, respectively to coated BSM while the K_(D)'s are 19 and 4.1 nM against TE. In both cases, TAB2.8 had ˜4-fold better affinity than TAB2.5 indicating that the vL-vH orientation in TAB2.8 is better than the vH-vL in TAB2.5. Expression was about 2-fold down for TAB2.8 compared to TAB2.5.

Having described the preferred embodiments of the present invention, it will appear to those ordinarily skilled in the art that various modifications may be made to the disclosed embodiments, and that such modifications are intended to be within the scope of the present invention. One skilled in the art would readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent. The molecular complexes and the methods, procedures, treatments, molecules and specific compounds are presently representative of preferred embodiments, are exemplary and are not intended as limitations on the scope of the invention. It will be readily apparent to one skilled in the art that varying substitutions and modifications may be made to the invention without departing from the scope and spirit of the invention.

All patents and publications mentioned in the specification are indicative of the levels of those skilled in the art to which the invention pertains. All patents and publications are incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference.

The invention may be practiced in the absence of any element or elements, limitation or limitations not specifically disclosed herein. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described (or portions), but it is recognized that various modifications are possible within the scope of the invention claimed. It should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention.

The invention has been described broadly and generically. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited. 

1. (canceled)
 2. An antibody-enzyme conjugate comprising: a. a scFv comprising heavy and light chains joined by a linker sequence, wherein said antibody-enzyme conjugate comprises a TAB 2.4 molecule comprising SEQ ID NO:8, TAB 2.6 molecule comprising SEQ ID NO:12 or a TAB 2.7 molecule comprising SEQ ID NO:13, and wherein the scFv is capable of specifically binding to TAG-72 antigen, and b. an enzyme conjugated to the scFv which is capable of converting a prodrug to an active drug.
 3. A composition comprising the antibody-enzyme conjugate of claim
 2. 4. The antibody-enzyme conjugate of claim 2, wherein the enzyme is a beta-lactamase.
 5. The antibody-enzyme conjugate of claim 4, wherein the beta-lactamase comprises the amino acid sequence set out in SEQ ID NO:4.
 6. The antibody-enzyme conjugate of claim 2, wherein the prodrug is a melphalan derivative, an auristatin, a camptothecin, a phosphate-containing prodrug, a thiophosphate-containing prodrug, a sulfate-containing prodrug, a peptide-containing prodrug, a D-amino acid-modified pro-drug, a glycosylated prodrug, a beta-lactam-containing prodrug, an optionally substituted phenoxyacetamide-containing prodrug, an optionally substituted phenylacetamide containing prodrug, a 5-fluorocytosine prodrug, or a 5-fluorouridine prodrug.
 7. The antibody-enzyme conjugate of claim 2, wherein the drug is an etoposide, a temposide, an adriamycin, a daunomycin, a caminomycin, an aminopterin, a dactinomycin, a mitomycins, a cis-platinum or cis-platinum analogue, a bleomycin, an esperamicin, 5-fluorouracil, melphalan, or a nitrogen mustard. 